Add optional automatic response body compression

This behavior can be enabled with the `compress` protocol option.
See the `compress_response` example for more details.

All tests are now ran with and without compression for both HTTP
and HTTPS.

examples/compress_response/src/toppage_handler.erl

@@ -0,0 +1,31 @@
+%% Feel free to use, reuse and abuse the code in this file.
+
+%% @doc Compress response handler.
+-module(toppage_handler).
+
+-export([init/3]).
+-export([handle/2]).
+-export([terminate/2]).
+
+init(_Transport, Req, []) ->
+	{ok, Req, undefined}.
+
+handle(Req, State) ->
+	BigBody =
+<<"A cowboy is an animal herder who tends cattle on ranches in North America,
+traditionally on horseback, and often performs a multitude of other ranch-
+related tasks. The historic American cowboy of the late 19th century arose
+from the vaquero traditions of northern Mexico and became a figure of special
+significance and legend. A subtype, called a wrangler, specifically tends the
+horses used to work cattle. In addition to ranch work, some cowboys work for
+or participate in rodeos. Cowgirls, first defined as such in the late 19th
+century, had a less-well documented historical role, but in the modern world
+have established the ability to work at virtually identical tasks and obtained
+considerable respect for their achievements. There are also cattle handlers
+in many other parts of the world, particularly South America and Australia,
+who perform work similar to the cowboy in their respective nations.\n">>,
+	{ok, Req2} = cowboy_req:reply(200, [], BigBody, Req),
+	{ok, Req2, State}.
+
+terminate(_Req, _State) ->
+	ok.