Fix SPARK-1256: Master web UI and Worker web UI returns a 404 error

Author: witgo <witgo@qq.com>

Closes #150 from witgo/SPARK-1256 and squashes the following commits:

08044a2 [witgo] Merge branch 'master' of https://github.com/apache/spark into SPARK-1256
c99b030 [witgo] Fix SPARK-1256
Bundle tachyon:  SPARK-1269

This should all work as expected with the current version of the tachyon tarball (0.4.1)

Author: Nick Lanham <nick@afternight.org>

Closes #137 from nicklan/bundle-tachyon and squashes the following commits:

2eee15b [Nick Lanham] Put back in exec, start tachyon first
738ba23 [Nick Lanham] Move tachyon out of sbin
f2f9bc6 [Nick Lanham] More checks for tachyon script
111e8e1 [Nick Lanham] Only try tachyon operations if tachyon script exists
0561574 [Nick Lanham] Copy over web resources so web interface can run
4dc9809 [Nick Lanham] Update to tachyon 0.4.1
0a1a20c [Nick Lanham] Add scripts using tachyon tarball