Added methods to CommonUtils

They come in handy across the code base
Fixed CommonUtils.concat check
More fixes to path manipulation functions
delete no use imports
Merge pull request #171 from scwf/deletenouseimports

delete no use imports
Reimplemented path manipulation function to use Apache FilenameUtils

We make sure all the FilenameUtil functions use the UNIX path separator,
which equals Constants.PATH_SEPARATOR
Updated documentation
Merge pull request #169 from manugoyal/common-util-additions

Added methods to CommonUtils
how to run tests
Merge remote-tracking branch 'btachyon/master' into loadufs
add multiple signatures for loadUnderFs; allow for any levels of  exclude prefixes; update loadufs docs