Add grunt release tasks

Summary:
- Add grunt release task. Run like "grunt release:v3.0.1"
- Uses grunt-contrib-compress - run this separately like: "grunt compress"
- Add "grunt clean" to remove release files

Resolves T251

Test Plan:
- Run "grunt compress", tgz and zip files are created in build/
- Run "grunt release:v3.0.1", build is run followed by compress with versioned filename
- Run "grunt clean" - build files removed

Reviewers: shadowhand

Reviewed By: shadowhand

Subscribers: eyedol

Maniphest Tasks: T251

Differential Revision: https://phabricator.ushahidi.com/D108