Merge static_world and web_server examples

The new example is called file_server and it's basically
the same as web_server was. The name is clearer than the
original, all examples being "Web servers".

The new example is also tested and the test suite has
been refactored a little.

examples/file_server/src/file_server_sup.erl

@@ -0,0 +1,23 @@
+%% Feel free to use, reuse and abuse the code in this file.
+
+%% @private
+-module(file_server_sup).
+-behaviour(supervisor).
+
+%% API.
+-export([start_link/0]).
+
+%% supervisor.
+-export([init/1]).
+
+%% API.
+
+-spec start_link() -> {ok, pid()}.
+start_link() ->
+	supervisor:start_link({local, ?MODULE}, ?MODULE, []).
+
+%% supervisor.
+
+init([]) ->
+	Procs = [],
+	{ok, {{one_for_one, 10, 10}, Procs}}.