Adds more cascading versions and updates latest version to 2.5.6
Merge pull request #151 from ajorgensen/add-more-cascading-versions

Adds more cascading versions and updates latest version to 2.5.6
Processed docsets/Cascading/cascading-2.5.6.tgz
Processed docsets/Cascading/versions/2.5.6/cascading-2.5.6.tgz
Processed docsets/Cascading/versions/2.2.1/cascading-2.2.1.tgz
Processed docsets/Cascading/versions/2.0.8/cascading-2.0.8.tgz
Processed docsets/Cascading/versions/1.2.6/cascading-1.2.6.tgz