Add consistent (by filename/path) sort on hashes

To avoid randomization in version control, it's best to have a
consistent order of results in the assethash JSON object between runs,
even if the source files don't change.

This commit adds a step to the file output process to re-order the JSON
object based on sorting the keys.
Fix jshint issues
Add tests for sorted output JSON objects

Given an input in an arbitrary order, confirm the output is sorted based
on filename.
Merge pull request #2 from dpolivy/bug/1

Add consistent (by filename/path) sort on hashes