Take `trailing` out since it got removed in jshint 2.5.0

https://github.com/jshint/jshint/releases/tag/2.5.0
Add a few more jshint option suggested by @pdehaan

https://github.com/mozilla/fxa-customs-server/issues/17#issuecomment-43251627
Check for unused variables

Dirty hack to silence a warning that is already fixed in #18.
Get rid of reserved words
Use grunt to run jshint and check for copyright headers
Merge pull request #19 from fmarier/issue17

Use grunt to run jshint and check for copyright headers (fix #17)