[Issue 85] by default, use http basic auth to include client credentials in requests

[samskiter]

Pretty self explanatory. as per #85 , we should no be putting client credentials in the request body. This is a rough port of a similar PR for AFOAuth2Client v1

[samskiter]

TODO: we could use NSURLCredential to do this.

[mattt]

Thanks for your PR, @samskiter. I ended up implementing this functionality in a slightly different way with 412d256. Please look for this in the forthcoming release.

[samskiter]

Brilliant, thank for your work on this @mattt

I should probably point out that the comment you added doesn't match with the way you implemented:

Initializes an `AFOAuth2Manager` object with the specified base URL, client identifier, and secret. The communication to to the server will use HTTP basic auth by default (use `-(id)initWithBaseURL:clientID:secret:withBasicAuth:` to change this).

should read:

Initializes an `AFOAuth2Manager` object with the specified base URL, client identifier, and secret. The communication to to the server will use HTTP basic auth by default (change the `useHTTPBasicAuthentication` property to change this).