Update "ubuntu-upstart" image with new "trusty"/"14.04" version

```console
root@79324b0231b7:/stackbrew/stackbrew# ./brew-cli --debug -b trusty-upstart --targets ubuntu-upstart git://github.com/tianon/stackbrew
2014-05-12 21:22:00,716 INFO Cloning docker repo from git://github.com/tianon/stackbrew, branch: trusty-upstart
2014-05-12 21:22:01,412 DEBUG ubuntu-upstart ---> latest: git://github.com/tianon/dockerfiles@e4b7cbaea20ba29771f6cbd427d4873abe54b3f4 sbin-init/ubuntu/upstart/14.04

2014-05-12 21:22:01,412 DEBUG Pulling ubuntu-upstart from official repository (cache fill)
2014-05-12 21:24:43,967 INFO [cache miss] 1293234046acde81a7a8f8cd71942dc8
2014-05-12 21:24:43,967 INFO Cloning git://github.com/tianon/dockerfiles (ref: e4b7cbaea20ba29771f6cbd427d4873abe54b3f4)
2014-05-12 21:24:44,883 INFO Building using dockerfile...
2014-05-12 21:24:51,251 INFO Committing to library/ubuntu-upstart:latest
2014-05-12 21:24:51,254 INFO Registering as processed: 1293234046acde81a7a8f8cd71942dc8
2014-05-12 21:24:51,254 DEBUG ubuntu-upstart ---> trusty: git://github.com/tianon/dockerfiles@e4b7cbaea20ba29771f6cbd427d4873abe54b3f4 sbin-init/ubuntu/upstart/14.04

2014-05-12 21:24:51,254 DEBUG Pulling ubuntu-upstart from official repository (cache fill)
2014-05-12 21:24:53,583 INFO [cache hit] 1293234046acde81a7a8f8cd71942dc8
2014-05-12 21:24:53,583 INFO This ref has already been built, reusing image ID
2014-05-12 21:24:53,583 INFO Committing to library/ubuntu-upstart:trusty
2014-05-12 21:24:53,586 INFO Registering as processed: 1293234046acde81a7a8f8cd71942dc8
2014-05-12 21:24:53,586 DEBUG ubuntu-upstart ---> 14.04: git://github.com/tianon/dockerfiles@e4b7cbaea20ba29771f6cbd427d4873abe54b3f4 sbin-init/ubuntu/upstart/14.04

2014-05-12 21:24:53,586 DEBUG Pulling ubuntu-upstart from official repository (cache fill)
2014-05-12 21:24:56,591 INFO [cache hit] 1293234046acde81a7a8f8cd71942dc8
2014-05-12 21:24:56,591 INFO This ref has already been built, reusing image ID
2014-05-12 21:24:56,591 INFO Committing to library/ubuntu-upstart:14.04
2014-05-12 21:24:56,594 INFO Registering as processed: 1293234046acde81a7a8f8cd71942dc8
2014-05-12 21:24:56,595 DEBUG ubuntu-upstart ---> precise: git://github.com/tianon/dockerfiles@e4b7cbaea20ba29771f6cbd427d4873abe54b3f4 sbin-init/ubuntu/upstart/12.04

2014-05-12 21:24:56,595 DEBUG Pulling ubuntu-upstart from official repository (cache fill)
2014-05-12 21:24:58,569 INFO [cache miss] 7866b895d2caff93d68ea6c6e9aa0d16
2014-05-12 21:24:58,569 INFO Cloning git://github.com/tianon/dockerfiles (ref: e4b7cbaea20ba29771f6cbd427d4873abe54b3f4)
2014-05-12 21:24:58,809 INFO Building using dockerfile...
2014-05-12 21:25:09,131 INFO Committing to library/ubuntu-upstart:precise
2014-05-12 21:25:09,134 INFO Registering as processed: 7866b895d2caff93d68ea6c6e9aa0d16
2014-05-12 21:25:09,135 DEBUG ubuntu-upstart ---> 12.04: git://github.com/tianon/dockerfiles@e4b7cbaea20ba29771f6cbd427d4873abe54b3f4 sbin-init/ubuntu/upstart/12.04

2014-05-12 21:25:09,135 DEBUG Pulling ubuntu-upstart from official repository (cache fill)
2014-05-12 21:25:13,018 INFO [cache hit] 7866b895d2caff93d68ea6c6e9aa0d16
2014-05-12 21:25:13,018 INFO This ref has already been built, reusing image ID
2014-05-12 21:25:13,018 INFO Committing to library/ubuntu-upstart:12.04
2014-05-12 21:25:13,027 INFO Registering as processed: 7866b895d2caff93d68ea6c6e9aa0d16
2014-05-12 21:25:13,027 DEBUG ubuntu-upstart ---> quantal: git://github.com/tianon/dockerfiles@e4b7cbaea20ba29771f6cbd427d4873abe54b3f4 sbin-init/ubuntu/upstart/12.10

2014-05-12 21:25:13,027 DEBUG Pulling ubuntu-upstart from official repository (cache fill)
2014-05-12 21:25:15,492 INFO [cache miss] 1e8298955c57ffff9429cf1ac61bb648
2014-05-12 21:25:15,492 INFO Cloning git://github.com/tianon/dockerfiles (ref: e4b7cbaea20ba29771f6cbd427d4873abe54b3f4)
2014-05-12 21:25:15,683 INFO Building using dockerfile...
2014-05-12 21:25:26,028 INFO Committing to library/ubuntu-upstart:quantal
2014-05-12 21:25:26,031 INFO Registering as processed: 1e8298955c57ffff9429cf1ac61bb648
2014-05-12 21:25:26,031 DEBUG ubuntu-upstart ---> 12.10: git://github.com/tianon/dockerfiles@e4b7cbaea20ba29771f6cbd427d4873abe54b3f4 sbin-init/ubuntu/upstart/12.10

2014-05-12 21:25:26,031 DEBUG Pulling ubuntu-upstart from official repository (cache fill)
2014-05-12 21:25:28,725 INFO [cache hit] 1e8298955c57ffff9429cf1ac61bb648
2014-05-12 21:25:28,725 INFO This ref has already been built, reusing image ID
2014-05-12 21:25:28,725 INFO Committing to library/ubuntu-upstart:12.10
2014-05-12 21:25:28,728 INFO Registering as processed: 1e8298955c57ffff9429cf1ac61bb648
2014-05-12 21:25:28,728 DEBUG ubuntu-upstart ---> raring: git://github.com/tianon/dockerfiles@e4b7cbaea20ba29771f6cbd427d4873abe54b3f4 sbin-init/ubuntu/upstart/13.04

2014-05-12 21:25:28,728 DEBUG Pulling ubuntu-upstart from official repository (cache fill)
2014-05-12 21:25:30,119 INFO [cache miss] b936402f34a097baa6e692ce02a928e6
2014-05-12 21:25:30,119 INFO Cloning git://github.com/tianon/dockerfiles (ref: e4b7cbaea20ba29771f6cbd427d4873abe54b3f4)
2014-05-12 21:25:30,356 INFO Building using dockerfile...
2014-05-12 21:25:40,640 INFO Committing to library/ubuntu-upstart:raring
2014-05-12 21:25:40,644 INFO Registering as processed: b936402f34a097baa6e692ce02a928e6
2014-05-12 21:25:40,644 DEBUG ubuntu-upstart ---> 13.04: git://github.com/tianon/dockerfiles@e4b7cbaea20ba29771f6cbd427d4873abe54b3f4 sbin-init/ubuntu/upstart/13.04

2014-05-12 21:25:40,644 DEBUG Pulling ubuntu-upstart from official repository (cache fill)
2014-05-12 21:25:42,963 INFO [cache hit] b936402f34a097baa6e692ce02a928e6
2014-05-12 21:25:42,963 INFO This ref has already been built, reusing image ID
2014-05-12 21:25:42,963 INFO Committing to library/ubuntu-upstart:13.04
2014-05-12 21:25:42,967 INFO Registering as processed: b936402f34a097baa6e692ce02a928e6
2014-05-12 21:25:42,967 DEBUG ubuntu-upstart ---> saucy: git://github.com/tianon/dockerfiles@e4b7cbaea20ba29771f6cbd427d4873abe54b3f4 sbin-init/ubuntu/upstart/13.10

2014-05-12 21:25:42,967 DEBUG Pulling ubuntu-upstart from official repository (cache fill)
2014-05-12 21:25:44,700 INFO [cache miss] b9281bfd05fec77c899bcb6f0906942e
2014-05-12 21:25:44,701 INFO Cloning git://github.com/tianon/dockerfiles (ref: e4b7cbaea20ba29771f6cbd427d4873abe54b3f4)
2014-05-12 21:25:44,948 INFO Building using dockerfile...
2014-05-12 21:25:55,983 INFO Committing to library/ubuntu-upstart:saucy
2014-05-12 21:25:55,987 INFO Registering as processed: b9281bfd05fec77c899bcb6f0906942e
2014-05-12 21:25:55,987 DEBUG ubuntu-upstart ---> 13.10: git://github.com/tianon/dockerfiles@e4b7cbaea20ba29771f6cbd427d4873abe54b3f4 sbin-init/ubuntu/upstart/13.10

2014-05-12 21:25:55,987 DEBUG Pulling ubuntu-upstart from official repository (cache fill)
2014-05-12 21:26:00,281 INFO [cache hit] b9281bfd05fec77c899bcb6f0906942e
2014-05-12 21:26:00,282 INFO This ref has already been built, reusing image ID
2014-05-12 21:26:00,282 INFO Committing to library/ubuntu-upstart:13.10
2014-05-12 21:26:00,285 INFO Registering as processed: b9281bfd05fec77c899bcb6f0906942e
2014-05-12 21:26:00,288 INFO BREW BUILD SUMMARY
-------------------------------------------------------------
OVERALL SUCCESS: True
-------------------------------------------------------------
ubuntu-upstart
-------------------------------------------------------------
 7 | OK | 6f26cbd2b731                                      
 5 | OK | 6f26cbd2b731                                      
 6 | OK | 6f26cbd2b731                                      
21 | OK | fc31a20b3d7a                                      
25 | OK | 162fde1a7ceb                                      
10 | OK | 901169da356a                                      
29 | OK | a6a5fd76d431                                      
26 | OK | 162fde1a7ceb                                      
30 | OK | a6a5fd76d431                                      
22 | OK | fc31a20b3d7a                                      
11 | OK | 901169da356a                                      
-------------------------------------------------------------
root@79324b0231b7:/stackbrew/stackbrew# docker images library/ubuntu-upstart
REPOSITORY               TAG                 IMAGE ID            CREATED              VIRTUAL SIZE
library/ubuntu-upstart   saucy               a6a5fd76d431        43 seconds ago       231 MB
library/ubuntu-upstart   13.10               a6a5fd76d431        43 seconds ago       231 MB
library/ubuntu-upstart   13.04               162fde1a7ceb        58 seconds ago       215.1 MB
library/ubuntu-upstart   raring              162fde1a7ceb        58 seconds ago       215.1 MB
library/ubuntu-upstart   12.10               fc31a20b3d7a        About a minute ago   196.8 MB
library/ubuntu-upstart   quantal             fc31a20b3d7a        About a minute ago   196.8 MB
library/ubuntu-upstart   precise             901169da356a        About a minute ago   247.5 MB
library/ubuntu-upstart   12.04               901169da356a        About a minute ago   247.5 MB
library/ubuntu-upstart   14.04               6f26cbd2b731        About a minute ago   384.6 MB
library/ubuntu-upstart   latest              6f26cbd2b731        About a minute ago   384.6 MB
library/ubuntu-upstart   trusty              6f26cbd2b731        About a minute ago   384.6 MB
```