Load shim from package name if no shim for moduleName.

[maxpeterson]

This is a possible fix for #310

The idea is to try and get the the shim for a module based on the package name in the case that the module name includes packageConfig.main.

In the case that you have a package

  {
      "name": "backbone",
      "location": "jam/backbone",
      "main": "backbone.js"
  }

then it would try and get shim['backbone'] if there was no shim['backbone/backbone']

[jrburke]

Thank you, merged. You can try latest master snapshot to confirm the fix:
https://raw.github.com/jrburke/r.js/master/dist/r.js