[SPARK-1198] Allow pipes tasks to run in different sub-directories

This works as is on Linux/Mac/etc but doesn't cover working on Windows.  In here I use ln -sf for symlinks. Putting this up for comments on that. Do we want to create perhaps some classes for doing shell commands - Linux vs Windows.  Is there some other way we want to do this?   I assume we are still supporting jdk1.6?

Also should I update the Java API for pipes to allow this parameter?

Author: Thomas Graves <tgraves@apache.org>

Closes #128 from tgravescs/SPARK1198 and squashes the following commits:

abc1289 [Thomas Graves] remove extra tag in pom file
ba23fc0 [Thomas Graves] Add support for symlink on windows, remove commons-io usage
da4b221 [Thomas Graves] Merge branch 'master' of https://github.com/tgravescs/spark into SPARK1198
61be271 [Thomas Graves] Fix file name filter
6b783bd [Thomas Graves] style fixes
1ab49ca [Thomas Graves] Add support for running pipe tasks is separate directories