Replace terminate/2 with terminate/3, adding a Reason

This should have been done a *long* time ago, back when I initially
added Websocket support. This is the first part of two in improving
loop handler support with regards to socket closure.

Reason may include: {normal, shutdown} for the most normal shutdown,
{normal, timeout} for a loop handler timeout shutdown, or {error, _}
if an error occured.

guide/http_handlers.md

@@ -16,7 +16,7 @@ this should be used for any initialization needs.
 The second callback, `handle/2`, is where most of your code should
 be. As the name explains, this is where you handle the request.
 
-The last callback, `terminate/2`, will be empty most of the time.
+The last callback, `terminate/3`, will be empty most of the time.
 It's used for any needed cleanup. If you used the process dictionary,
 timers, monitors then you most likely want to stop them in this
 callback, as Cowboy might end up reusing this process for subsequent

guide/introduction.md

@@ -87,7 +87,7 @@ handlers, Websocket handlers, REST handlers and static handlers. Their
 usage is documented in the respective sections of the guide.
 
 Most applications use the plain HTTP handler, which has three callback
-functions: init/3, handle/2 and terminate/2. Following is an example of
+functions: init/3, handle/2 and terminate/3. Following is an example of
 a simple handler module.
 
 ``` erlang
@@ -96,7 +96,7 @@ a simple handler module.
 
 -export([init/3]).
 -export([handle/2]).
--export([terminate/2]).
+-export([terminate/3]).
 
 init({tcp, http}, Req, Opts) ->
     {ok, Req, undefined_state}.
@@ -105,7 +105,7 @@ handle(Req, State) ->
     {ok, Req2} = cowboy_req:reply(200, [], <<"Hello World!">>, Req),
     {ok, Req2, State}.
 
-terminate(Req, State) ->
+terminate(Reason, Req, State) ->
     ok.
 ```
 

guide/loop_handlers.md

@@ -31,7 +31,7 @@ practice is known as server-sent events.
 
 Loop handlers essentially wait for one or more Erlang messages
 and feed these messages to the `info/3` callback. It also features
-the `init/3` and `terminate/2` callbacks which work the same as
+the `init/3` and `terminate/3` callbacks which work the same as
 for plain HTTP handlers.
 
 The following handler waits for a message `{reply, Body}` before
@@ -46,7 +46,7 @@ this message.
 
 -export([init/3]).
 -export([info/3]).
--export([terminate/2]).
+-export([terminate/3]).
 
 init({tcp, http}, Req, Opts) ->
     {loop, Req, undefined_state, 60000, hibernate}.
@@ -57,6 +57,6 @@ info({reply, Body}, Req, State) ->
 info(Message, Req, State) ->
     {loop, Req, State, hibernate}.
 
-terminate(Req, State) ->
+terminate(Reason, Req, State) ->
     ok.
 ```