Add Instagram Provider

[Waynenabors]

My first pull request so hopefully it makes sense.
This was started on the old repo here: https://github.com/NoamB/sorcery/pull/625/files

We are using this code with an approved Instagram client_id with public_scope and it works great.

[Ch4s3]

@Waynenabors Sorry for the delay! @athix What are your thoughts on rolling this our vs making it a separate gem?

[Waynenabors]

Fixes an issue where new Facebook Apps with API v2.8 are no longer compatible with v2.2 Oauth callback content/type. Starting with v2.3 the response is valid JSON. So if we can pick our API version we should be able to pick our parser. I would even make the argument that it should default to :automatic since that works now. But for now I just needed access to set config.facebook.parse.

[mzp]

Fixes an issue where new Facebook Apps with API v2.8 are no longer compatible with v2.2 Oauth callback content/type.

I met this problem (and monkey patched). I appreciate if this facebook's changes are merged.

[Ch4s3]

If someone can resolve the conflict, I'll merge this.

[joshbuker]

Last update almost year ago, whoops. 😬