shearl: s/GOAWAY/GO_AWAY, s/REFUSED_STREAM/RETRY_STREAM, s/RST_STREAM/TERMINATE_STREAM

renamed GOAWAY to GO_AWAY to be consistent with the naming for other two-word frame types ie RST_STREAM, PUSH_PROMISE and WINDOW_UPDATE

s/REFUSED_STREAM/RETRY_STREAM The definition of REFUSED_STREAM is somewhat contradictory with the definition of the word refused. The word refused is defined as: indicate or show that one is *not willing* to do something (https://www.google.at/).  The definition of REFUSED_STREAM in Section 7 references section 8.1.4 which says that a REFUSED_STREAM is safe to retry.  In other words the server is actually *willing* to process the stream, but *currently unable* (e.g. because the client overran settings and so the client needs to retry the stream with the new settings.)

s/RST_STREAM/TERMINATE_STREAM The definition of RST_STREAM doesn't match the meaning of the word reset.  The word reset generally means: "cause (a binary device) to enter the state representing the numeral 0." [http://www.oxforddictionaries.com/definition/english/reset] In other words, the word reset implies that the stream should be reset back to its *original* state (i.e. IDLE), but RST_STREAM immediately takes a stream to its *terminal* state (i.e. CLOSED).