Add plugin for Sencha Touch.

Should be able to check for:
  Sencha 0.9 beta
  Sencha 1.0
  Sencha 1.1.0+
  Sencah 2.0.0+
If all else fails, look for sencha in script@src
Merge pull request #26 from miketaylr/sencha-plugin

Add plugin for Sencha Touch.