Fix Grunt dev

Grunt wasn't rebuilding the tmp version in the watch task, I just switched watch and dev to run the test task.

**Changes:**
- Make grunt `dev` task use the existing `test` task
- Make grunt `watch` task use the existing `test` task

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Ref: https://github.com/marionettejs/backbone.marionette/pull/1188#issuecomment-40645332