added Ensure call to constructor
:lipstick: cleaned up usings
added basic tests for OAuth1TokenRequest
moved tests into v1 folder
moved long-running integration tests into own folder so they can be run separately from "normal" unit tests
moved common test data into static TestData class
:lipstick: gave tests more descriptive names
added required properties as constructor parameters to OAuth1AccessRequest
changed SignatureMethod to an enum

I find it clearer to use an enum in situations like this, as opposed to
a set of string constants
moved common functionality into OAuth1Request.SubmitRequest()
changed exception type thrown by GetHash() if unsupported
:lipstick: updated param names, docs
moved (still commented out) code for generating nonce and timestamp to OAuth1Request
moved Token & TokenSecret into OAuth1AccessRequest, refactored SignRequest()
changed back to using string constants for signature method, updated docs
cleaned up commented out code from last commit
added signatureMethod param to test so it could be used to test both methods
fixed implementation of HMAC-SHA1, added tests
heavy refactoring to move base functionality into static OAuth1 class
made Version property public so it gets included in parameters (though technically it's optional)