Move jshint options into a separate file

When jshint is called from the shell it looks for in it's own directory and
then recursively up for a .jshintrc configuration file.

By moving the jshint options into a separate file the config can be shared
by grunt and jshint, so that jshint can be called directly.
Merge pull request #104 from maurizi/topic/jshint

Move jshint options into a separate file