Feature: Remove loaders from file prefixes.

[ryan-roemer]

Resolve identifiers better for things like:

$ node bin/inspectpack.js -s test/fixtures/loaders/dist-development-4/stats.json -a sizes | grep "\!"
* /Users/rye/scm/fmd/inspectpack/node_modules/css-loader/index.js!/Users/rye/scm/fmd/inspectpack/test/fixtures/loaders/src/style.css
* /Users/rye/scm/fmd/inspectpack/node_modules/raw-loader/index.js!/Users/rye/scm/fmd/inspectpack/test/fixtures/loaders/src/hello.txt

• Handle _isNodeModules inference correctly ( PR BUG: Fix inference of node_modules for loader prefixes. #99 )
• Potentially add another field for "path" or something. Would work for both node_modules and app source.
• Check and test on Mac.
• Check and test on Windows.