Fixed websockets handling on the scenario side

Removed specific websocket code to use main ws.WebSocket
Now websocket messages in the backlog can be flushed if needed.
Added signal handling in griotte.graceful.
Handles websocket connection delays so subscriptions are not sent before
the socket is really ready.
Added a bit of documentation.
[wip] Adds static Expecter instance

Added method to retrieve a static Expecter instance.
This code will be removed, a singleton will be used instead.
Turned Expecter into a singleton

Since the scearion is played sequentially, we just need one instance of
Expecter.
Changes installation files and make targets

Changed make targets so griotte can be installed system-wide. This is
almost necessary since RPIO doesn't work in virtualenv unless you run
inside your virtualenv as root (this means that sudo griottte/bin/gpio
is not a solution).
Added some kind of prefixed targets : make virtual.dev will install
dev dependencies in a virtualenv, while make install.dev will install
dev dependencies system-wide. Ditto for prod.
Added MANIFEST.in and changed setup.py to include static files. However,
they are not installed with `python3 setup.py install`. Needs more
digging.
Added init script skeleton.
Added config file with a new format, not yet handled by the library.
Changed part of installation instructions, but they need to be reworked
quite a lot when installation method gets stable.
Adds gpio handling

Added preliminary gpio server code.
Adds config module

Added config module that handles tornado.options handling.
Fixes options usage here and there
More tries for setup.py and more docs

More unsuccessful tried for data_files in setup.py
Added more docs about profiles
Fixed Makefile for _devel and _production targets
Renamed channel to port in GPIO handler to avoid confusion
Implements scenario digital methods and Expect

Fixed DigitalHandler
Fixes indentation in Expect
Changes _ to - in config options

Moved from '_' to the more natural '-' in config variables names