Make AMD module id's optional
Make module id's for AMD body in UMD optional as well
Improve performance
Merge branch 'master' of github.com:6to5/6to5 into amd-module-id

Conflicts:
	lib/6to5/file.js
	lib/6to5/transformation/modules/umd.js
Reuse Formatter::getModuleName(), fix opts
Revert "update umd and amd tests with new moduleName option"

This reverts commit 5409691a3a63290ff7c7013035ec1b351e1eb250.
Update docs
Rename to "--amd-module-ids"
Merge pull request #190 from webpro/amd-module-id

Make AMD module id's optional