Switch to Pathname to determine file locations:

 - Allows Jently to be run from directories other than the root.
 - Allows Jently to run on platforms other than UNIX.
Modify the load path to include lib/ to simplify requires
Expand logged backtraces across multiple lines, to improve readability
Provide actionable feedback if Jenkins doesn't know about a job
Make specs pass
Merge pull request #33 from auxesis/master

Reduce friction for new users