do not write StatusText in error case

It doesn't get appended to the HTTP status line, it is part of the
body.  This results in the body not being valid JSON.

Fixes issue #13.
HandleAccessRequest: Fix nil-pointer dereference on missing authorization
Merge pull request #17 from yext/master

HandleAccessRequest: Fix nil-pointer dereference on missing authorization
handleRefreshTokenRequest: Fix nil-pointer
handleRefreshTokenRequest: if set, scope must be the same as the previous token
Revert previous commit
Merge pull request #18 from yext/master

handleRefreshTokenRequest: Fix nil-pointer
Merge pull request #13 from joeshaw/issue-13

Writing status text breaks JSON decoding
* Passord example only work with GET request, must allow in server

fixes #14
* GoAuth2 now sends client secret on Basic Auth, no need to allow it on params any more.

fixes #16
* Add OSINCLI sample
* Add ResponseJSON tests
* Authorization tests
* Authorization and info tests
* Access token tests
* Add ASSERTION grant_type as defined in http://tools.ietf.org/html/draft-ietf-oauth-v2-10
* Return client_id by default on info request, so the application knows if this token is for its client_id
* Internal error messages for obscure errors
Add Error Messages in Returned Error.
Merge Changed from Upstream.