Implements PLAINTEXT and HMAC-SHA1 signatures of oauth spec http://oauth.net/core/1.0a#signing_process
The signature method which will be used to sign requests.
Functions to sign requests according oauth spec.
The signature method to use
The consumer secret
|-> Maybe String|
The token secret
For a given request, this function is able sign it using the method specified. The full description of this process is described in depth at http://oauth.net/core/1.0a#signing_process.