Revert "MOBI-850 - 401 is better than 402 and more consistent too"
Reverting this so NeatMobile 2.0 clients can display more useful error messages that explain why auth has failed

This reverts commit 5194ed4dbbc645e95d29841715ae8fd721f15bc1.
Merge branch 'master' of github.com:TheNeatCompany/rack-oauth2-server