Rename ``define`` function to ``defineLanguageRule``

``define`` causes issues when trying to use with RequireJS which means it can't be loaded as an AMD module using the shim config. It also breaks when trying to optimize using r.js & uglify/uglify2.

``defineLanguageRule`` is a more descriptive name also.
Merge pull request #2 from owilliams/patch-1

Rename ``define`` function to ``defineLanguageRule`` to avoid RequireJS issues