Update the library to support the OAuth 2.0 authorization

[suhoij]

I've added the "Authorization" header in order to support OAuth 2.0 authorization flow.

[jzabel]

@suhoij - thanks for suggesting this change to support Hubspots OAuth 2 functionality. Some suggestions on the fix.

Per their docs, you should only send it in the auth header (oauth) or on the string (hapikey): http://developers.hubspot.com/docs/methods/oauth2/using-access-tokens
It seems the old oAuth on the string is deprecated: http://developers.hubspot.com/docs/methods/auth/oauth-overview

Can you adjust to put this into the headers construction that gets passed in as a group? Moving up the auth params and updating comments? Plus removing the inclusion on the URL string itself as per the new docs?

[suhoij]

@jzabel Sure. I could clean it up to correspond only the latest API.

[suhoij]

@jzabel I've removed the authParams and moved the api_key to the finalParams. Also the comment was updated. Please, check.