fix(js): Fix typo in String.prototype.md5()

[tomushkin]

The minified String.prototype.md5() implementation is missing a couple of backslashes in replace(s/rn//g, "n") causing contacts that contain "rn" to not have the gravatar displayed.

Also it's doing toLowerCase() on its input, which doesn't seem correct.

[WoodySlum]

Hi !

Thank you for your contribution
I would prefer to do email.toLowerCase().md5().toLowerCase() instead of, modifying common.js. I didn't see any other use of md5 string prototype, but it may be the case in the future.

[tomushkin]

Hello, the inner md5 function already does toLowerCase() on the hash. The public function does it on the input which must be a mistake:

  var md5 = function(s){...; return i.toLowerCase();};
  return md5(this.toLowerCase());

I moved the second call from this to email, which effectively is what you are suggesting?