Minor stuff.
Type name sanification.
Persistent Raft state.

Now Raft stores own state in a persistent storage. This commit should fix the following bug: a node may vote twice in the same term, when it restarts and forgets about the previous vote.
Fix a data race and segfault.

* Configuration machine uses proper reactor now. Before I accidentally passed wrong reactor to it, so my single-threaded code runned in two threads actually.
* Don't remove service client from the callback. As I know, most Cocaine IO objects shouldn't be deleted from the callbacks called by them. The service client is not an exeption from this rule.
* Unbind a readable_stream when an socket error occurres. It's because we don't want receive any events and anything with an invalid stream.
Don't send heartbeat if an append request is already scheduled to be sent.
Fixed serialization of raft::command_result.

Command_result should provide address of the actual leader, but I forgot to serialize it.
Some comments and log messages.
Don't cancel just posted error.

It was a good idea to stop watching a socket when a socket error occurs.
But it's a bad idea to cancel the callback which should notify about the error.
Merge pull request #119 from andrusha97/raft-bugfixes

Persistent RAFT state and bugfixes
Fix broken assignment operator.
Merge pull request #120 from 3Hren/patch-2

Fix broken assignment operator.
Synchronized with Blackhole v0.2.

 - There is no longer need for explicit logger synchronization. Logger is thread-safe by default.
 - Cocaine should no longer format debug messages with `0` verbosity.
 - Less code needed for conversion between `dynamic_t` and Blackhole's internal objects for external configuration.
Insert intermediate namespace for Cocaine keywords.
Merge pull request #121 from 3Hren/master

Synchronized with Blackhole v0.2.
Mother of all commits.
Recursive slot support.
Fixed build errors from GCC 4.8.
Fixed build errors from GCC 4.6.

Apparently, GCC 4.6 can't compile std::shared_ptr<const T>.
Updated sample configration.
Disable cluster links w/o Gateway.