Grunt automation of build/tag/publish

Filer's build process was a multi-step process, and grunt is powerful enough to automate it. Now we have :)
Updated CONTRIBUTING.md to include instructions on grunt publish.

This significantly changed the workflow, so I wanted the changes to be clear.
Merge pull request #188 from sedge/issue-71

Fixes #13
Merge branch 'develop' into Issue145
Changed position of mode check