Remove outdated comments, all edoc, plus a few minor tweaks

src/cowboy_sub_protocol.erl

@@ -13,21 +13,6 @@
 %% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 %% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
-%% @doc Behaviour for sub protocols.
-%%
-%% Only one function needs to be implemented, <em>upgrade/4</em>.
-%% It receives the Req, the environment, the handler that the request has been
-%% routed to and the handler's options. It acts exactly the same as a
-%% middleware, so returns the same values a middleware's execute/2.
-%%
-%% Once the sub protocol has processed the request it should add the result
-%% to the environment. This is done by adding the tuple {result, Value} to the
-%% environment list. To continue handling requests on the current connection the
-%% Value should be the atom ok. Any other value will prevent the processing of
-%% subsequent requests.
-%%
-%% <em>upgrade/4</em> will be called when a handler's init/3 returns
-%% {upgrade, protocol, Module}, where Module is the module of the sub protocol.
 -module(cowboy_sub_protocol).
 
 -callback upgrade(Req, Env, module(), any())