Allows passing extra headers to the Client Credentials strategy

[nikz]

Hiya,

This fixes (what I think) is a wee bug with the client_credentials grant where it won't allow passing through extra headers to the token request.

It includes a passing spec, although I'll be the first to admit it's a little hacky... any guidance there appreciated.

I also didn't add any documentation since it's a bugfix, and there's language to that effect under Authorization Grants but happy to do that if you'd like.

Cheers!

Nik

[coveralls]

Coverage increased (+0.03%) to 96.591% when pulling a66534f on nikz:allow-passing-extra-headers-to-client-credentials into 7691a2c on intridea:master.

[thedarkside]

I ran into the same issue. It is a bug!

[djberg96]

Seems like this ought to be merged. The failures appear to be JRuby and/or Ruby 1.9.x or earlier only.

[josephpage]

Hey @nikz,
The gem now has a new team of maintainers. 🎉
I'll be happy to merge your PR when the conflits will be resolved.

[nikz]

@josephpage Great! I thought I made the change just now, but it seems Github isn't happy with it so I might have to do it properly instead - give me some time and I'll get it fixed up for you.

[pboling]

You will need to rebase on latest master in order to resolve the conflicts.

[nikz]

@pboling @josephpage I actually think this has been fixed by this change. We could include the spec to verify it doesn't break again if you'd like (happy to adjust the PR), or feel free to close this PR.

Thanks!

[pboling]

@nikz Yes, great idea. More specs is great! I will extract the spec and merge it, unless a wild PR appears before I get to it. ;)

[nikz]

@pboling sent up #381 for you, so I'll close this one up now. Cheers!