Error: Cannot find module 'uberscore'

Hey there, so `uberscore` was added as a devDependency in [this commit](https://github.com/aearly/grunt-urequire/commit/726219ba4c8d87d92291c325be5a367c85927ef8#L1R51).  But it's also being used in the task [here](https://github.com/aearly/grunt-urequire/commit/726219ba4c8d87d92291c325be5a367c85927ef8#L2R6).  Since it's just a devDependency, it doesn't get installed for someone using it in like a package.json file.  I suppose it could be just put into "dependencies" and solve this.