Migrate finagle-thrift/finagle-stream tests to ScalaTest

In preparation for 2.11.x finagle-thrift tests will migrate to ScalaTest


Remaining Work:
1) Finagle-Streams
2) 2.11.x testing
3) Conversation about FinagleClientThriftServerSpec structure
4) Renaming tests from *Spec -> *Test
5) Clean up commit history and conform to commit message standards
This indentation's a bit weird. Let's use:

    case class MyStreamResponse(
      httpResponse: HttpResponse,
      messages: Offer[ChannelBuffer],
      error: Offer[Throwable]
    ) extends StreamResponse {