Enable compression for Tsv, Csv, etc.

Enable compression for delimited scheme outputs. 

> Method setSinkCompression sets the sinkCompression of this TextLine object. If null, compression will remain disabled. 

Cascading automatically disables the compression when sinkCompression set to null.
With sinkCompression set to 'TextLine.Compress.DEFAULT' one can specify the compression on job configuration.
Some Execution fixes
Merge branch 'develop' of https://github.com/twitter/scalding into develop

Conflicts:
	scalding-core/src/main/scala/com/twitter/scalding/FileSource.scala
Update Cascading JDBC Version to 2.5.4.
Merge FileSource.
well that explains why hRaven estimates were backwards
Merge pull request #1007 from twitter/execution-fixes

Some Execution fixes
Merge pull request #1016 from morazow/update/cascading-jdbc

Update Cascading JDBC Version.
Merge pull request #1018 from twitter/bholt/oops

Fix hRaven Reducer Estimator