Introducing new asynchronous generator classes. Chain is dropped forever.

 `Deferred` class is an extension of twisted deferreds with ability to generate more than one chunk, which is cool for Cocaine.

  - provided new decorators (replacing for chain.source). Note, that functions decorated with new decorator are no longer returns the last result from `yield` expression - you should manually return result as like it is usual function using special function `return_` (or return statement for python 3.3)
  - services can now correctly parse recurring api (with `null` provided meaning that state is recurring).
  - `Future` is a simple wrapper over python 3.3 or tornado futures. You are not restricted with future choice.
PEP-8 style.
Service is now located in `services` module.

 - deprecated test has been removed.
Todo added.
Major changes in service api.

 - Module `message` has been reviewed - added additional namespaces to the RPC protocol definition.
 - ChokeEvent has been changed its location.
 - Locator is now can be officially reached via import
 - Some naming refactoring done.
 - Service implementation has been changed to match new deferred system.
 - States and Sessions added to match new cocaine StateMachine-like API.
Configuring deferred class to match protocol.

 - Bugfix: protocol attributes updated.
 - Deferred engine no longer closes its deferred on any error (including ChokeEvent).
 - There are special deferred called `CocaineDeferred` to emit ChokeEvent on channel finishing when there were at least one chunk, otherwise to simply close channel.
Deferred testing.

 - Useful testing mocks added.
 - A huge pack of deferred generator tests added.
Framework server-side has been refactored.

 - `Request` and `Response` classes are represents (suddenly) worker request and response. Request only keeps associated deferred inside it and provides access to it. Response has methods to control response from worker to cocaine-runtime.
 - Temporarily disable client auto-reconnect and timeouts.
 - Echo example updated.
Another chunk of server-side refactoring done.

  - Some refactoring done over decorators - styling, package decomposition.
  - Sandbox class moved to the separate file.
  - Relative importing idiom are in progress.
  - Examples has been updated.
Drop deprecated example.
Session now provides associated deferred with it.

 - echo example updated.
Package decomposition.

 - Module `message.py` are placed with other protocol stuff.
Module decomposition done over service classes.

 - Locator is moved to the separate file.
 - AbstractService and Service has been splitted.
 - Useful decorators and context managers moved to the `internal` module.
Portability change.

 - using builtin function `zip` instead of `izip` makes code more portable with python 3.
 - tiny styling done.
Protocol messages renaming.
Code cleaning over protocol messages.
Fix attribute mismatch.
Fixed bug with worker type mismatch.

 - on termination, worker died because an internal exception raised.
Protocol message review.

 - Drop metaclass definition in favor on usual initialization method.
Drop unused file.