Update tests/frontend devDependencies

* grunt-contrib-jshint: v0.8.0 to v0.9.2
  - https://github.com/gruntjs/grunt-contrib-jshint/blob/v0.9.2/CHANGELOG
  - Minor changes and bug fixes
  - Lastest version is v0.10.0, but that embeds jshint v2.5.0
    which we don't want to use yet.

* grunt-contrib-watch: v0.5.3 to v0.6.1 (latest)
  - https://github.com/gruntjs/grunt-contrib-watch/blob/v0.6.1/CHANGELOG
  - Minor changes and bug fixes

* grunt-jscs-checker: v0.4.0 to v0.4.1 (latest)
  - https://github.com/gustavohenke/grunt-jscs-checker/compare/0.4.0...0.4.1
  - Minor changes

Change-Id: I68e9057f8e353e2c3ac8b889977de07597211c54
Merge "Update tests/frontend devDependencies"