Added a maven style example with a single top level directory

This example shows a problem when you try to build with a BUILD file one level deep

```
$ cat at maven-example/BUILD
jvm_binary(name='maven-example',
  source='src/main/java/example/Main.java',
  main='example.Main'
) 
```

 and try to invoke pants on the default target in that file:


```
PANTS_DEV=1 ./pants goal binary maven-example
*** Running pants in dev mode from /Users/zundel/Src/Pants/src/python/pants/bin/pants_exe.py ***

14:59:46 00:00 [main]
               See a report at: http://localhost:57641/run/pants_run_2014_05_27_14_59_46_615
14:59:46 00:00   [bootstrap]
14:59:46 00:00   [setup]
14:59:46 00:00     [parse]
               Unknown goal(s): maven-example
               
               FAILURE
```

It works correctly if you add a slash on to the end of the name:

```
PANTS_DEV=1 ./pants goal binary maven-example/
*** Running pants in dev mode from /Users/zundel/Src/Pants/src/python/pants/bin/pants_exe.py ***

14:58:56 00:00 [main]
               See a report at: http://localhost:57641/run/pants_run_2014_05_27_14_58_56_486
14:58:56 00:00   [bootstrap]
14:58:56 00:00   [setup]
14:58:56 00:00     [parse]
...
               SUCCESS
```

or if you fully specify the target as "./pants goal binary maven-example:maven-example