Improve ember casper test stability

fixes #3171, fixes #2382, refs #3130

- Moved grunt init from travis into grunt validate, this makes sure we get verbose output from grunt init.
- Added `grunt test` task to run just the tests without building if you want
- Upgraded grunt-contrib-concat and added nonull property (had to switch to src/dist for this to work) #2382
- Upgraded bower to 1.3.5, which appears to resolve #3171
- Changed bower git assets to all be referenced the same and removed resolutions again #3130