For issue #329. Adding feature for stash functionality, enabling working on multiple computers
added requirement for stash.rb to exercism.rb
removing junk line from api.rb
stash_name field added to submission, now able to save a stash file for each exercise based on filename. Superseding stash saves will delete old stash file, and new submission attempts will delete stash file matching that exercise. Also added endpoint for /stash/list to return list of all saved stash submissions.
fixed merge conflicts
Needed to add stash.rb to use_cases.rb, and including initial tests. Will work on adding to them later
Merge pull request #541 from kevinml/add_stash

Stash a submission for use on multiple computers (#329)