Remove control characters and add docs

1. Removed control characters that cause JSHint warnings.
   They appear in the source file in m17n, but serve no
   clear purpose, and the author cannot be reached.

2. Added the URL to the original m17n source code.

3. Added comments. They are in the beginning of the line
   to avoid the inconvenient RTL alignment of those lines,
   which many editors do automatically.
Merge pull request #251 from amire80/ur-phonetic-control-chars

Remove control characters and add docs