Updated module_name regexp to not match incorrect indexes

[Caleb-T-Owens]

• Closes files ending in _index.js have index replaced with an empty string #215

This updates the regex used to identify index files to ensure that modules like foo/special_index don't get mapped to foo.

The cause of the problem was that the previous regex matched 1 or 0 / characters, which meant anything followed by index and the end of the string, would qualify. We now ensure that we match either the start of the string or /

[mylons]

looks good to me! looks better than my solution i think: mylons@c5cb32b