Improve guide on listening on privileged ports

Making people happy one IRC channel at a time.
Return {error, badarg} if start_listener got a bad transport module
Add {socket, Socket} transport option, for accepting on existing sockets
Merge branch 'adt-socket-transport-opt' of git://github.com/basho/ranch
Make listener supervisor failures less painful

Two general issues were addressed. The first one is the issue with
statically defined pids passed into childspecs. This issue prevents
regular supervisor' children restarts in the case of someone's
failure.

The second one is the not quite appropriate restart strategy.
Changed to rest_for_one which in pair with previous fixes assures
that live connections will not die in the case of partial failure.
Among possible failures are listening socket shutdown or frequent
accept errors.
Fix for cases when listener dies before acceptors
Test cases for the listener supervisor behavior
Ensure transport module is loaded before checking exports

Tests were constantly failing without this patch. It seems ct
starts erlang code server in interactive mode, so application
module loading is defered.
Assure we manually close right socket in testcases

Concerning supervisor tests subtle issue. Before we just presumed that last
port in the global list of ports is the listening socket. From now we trace
the return value of the `ranch_tcp:listen` call.
Merge branch 'fix/listener_sup_failures' of git://github.com/keynslug/syncranch
Add ranch:set_max_connections/2 and get_max_connections/1
Improve max_connections type

It is non_neg_integer() | infinity. Introduce the type
`ranch:max_conns/0` for easier manipulation.
Update ROADMAP
Update AUTHORS
Add #ninenines IRC channel + support options to the README
Update version to 0.6.0
Allow raw socket options for TCP and SSL

This patch lets the user set and use raw socket options as described in
inet:setopts/2 documentation.

The raw options can be useful to use TCP features that are platform-
specific and not supported in inet in general, such as TCP_DEFER_ACCEPT
or TCP_LINGER2 in linux stacks, for example.
Merge branch 'master' of https://github.com/ferd/ranch
Ignore tracking of requests when MaxConn = infinity

There is no need to contact the server and track requests unless being
asked to do so by the user. It's going to be faster and more efficient
to not track anything when being told tracking doesn't matter.

Whenever the max connections is set to infinity, the connections
counting key is not created, or is deleted if it existed already.
When using a numeric value, the connection count is created or
maintained if it existed already.

Moreover, trying to reduce a listener's counter while the max connection
number is set to `infinity` will return 0 and avoid all counting
operations as they are meaningless.
Merge branch 'optimise-conn-count' of https://github.com/ferd/ranch