Close GH-20: Use single top .js file if no bower main

- Checks for a single top level js file, excludes .min. If it finds more than 1 js file it will leave the original value in place.
Merge pull request #26 from robdodson/missing-main

Close GH-20: Use single top .js file if no bower main
Merge branch 'master', remote-tracking branch 'upstream/master'