OTWO-3248: Convert Ohloh SCM into a gem

The function url_regex needs to match "@" in urls to support Ohloh's
tests. Since rvm gem paths will have gemset@ruby pattern, @ can be a
part of url for repositories inside this library's test folder.

In Ohloh's integration tests we try to [reuse the ohloh_scm test repositories](https://github.com/blackducksw/ohloh/blob/10058b71e98e0b7ea2f05af993edd3bcfce114fa/test/integration/complete_suite_test.rb#L18). After the conversion to gem, the scm's test repositories will be under gem path. If rvm is being used, the path will have @.

Since ohloh_scm wants to allow local file paths as repository urls and @ is a valid part of filename, I believe ohloh_scm must support it.