Proper HTTP response codes for errors

[jasonclemons]

The responses for errors feel a bit mixed up, for example https://www.xboxleaders.com/api/2.0/games.json?gamertag=Major%20N!elson will return an error telling us the user doesn't exist with a 200 response code. It feels like it should be a 404 with the same message. Likewise for achievements and games. In cases where there is a problem like an invalid value perhaps a 400. The messages themselves are good but using HTTP responses consistently would be better for the end-user.

-- Sent via email

[djekl]

This is now achieved via the pull request above.

To change the output code given change it in the list of error codes