GetFiles issues

Only 2 arguments passed in to GetFiles but it was expecting 3 thus “cb”
was undefined…

File System GetFiles should handle empty “entries” array properly…
Allow the Sample to easily changed providers
Update index.js

Took suggestion from Raymond...
Update storage-service.js

Took Raymond's suggestion...
Merge pull request #32 from tonysoft/master

Issues involved in "getFiles"