Remove the unused wrappers/ directory.

This was an artifact left over from the Brigade days.
Implement util.{absolut,relativ}ize for processing module identifiers.
Add a test of @providesModule directives.
Make lib/relative.js aware of canonical module identifiers.
Make reader.readModuleP return canonical modules, with tests.
Remove duplicate modules from the output of readMultiP.

Closes #5.
Test getRequiredP with @providesModule.
Bump NPM version to 0.6.6 in preparation for publishing.
Merge pull request #21 from benjamn/issue-5-avoid-duplicate-modules

Avoid duplicate modules