Convert all the request for the mapping to one

So if the request come as `en-ca` or `en-CA` it will work for both
Currently if we set the mapping `"en-CA": "en-US"` it will only work for that case letter
this will allow us to get it work for both
0.2.8
Fixed typos of "langauge" -> "language" in README.md.
Merge pull request #19 from toolness/patch-1

Fixed typos of "langauge" -> "language" in README.md.