Add support for browser field in package.json

Based on the unofficial spec
https://gist.github.com/defunctzombie/4339901
Map false to a blank module
Add tests for browser field handling in npm metadata
First sketch of the tests for createMapper
Add author to blank and createMapper
Normalize the modules in browser map based on the package root
Don't use the versioned uids in the mapper
Move the uid parsing logic into createPackageMapper module
Improve npm cralwer browser field tests
Rename moduleName to name
Make uid.getName handle both module uids and names
Rebuild rave
Merge pull request #37 from KidkArolis/browser-field

Add support for browser field in package.json.
Also adds support for module name mapping which could be leveraged in other ways.