Implemented chmod command along with documentation and unit tests.  Github issue 35
Include unit tests.
Add unit test directory stucture.  Sorry, new to git.  Forgot that it has no support for empty directories.
To fix travis-ci build issues, try to focus tests on the bits that changed to reduce the likelihood of umask issues.
Move bitmask constants into a PERMS namespace per code review feedback from @arturadib.
Merge pull request #48 from brandonramirez/chmod

Implemented chmod command.  Github issue 35