[General] Minor improvements.
[RPC] Upstream transitions.
Merge branch 'master' of https://github.com/cocaine/cocaine-core

Conflicts:
	src/logging.cpp
[Logging] Migrate to new Blackhole version.
Merge pull request #147 from 3Hren/master

[Logging] Migrate to new Blackhole version.
[Common] Drop boost::asio in favor of pure asio.

This change allows to build cocaine runtime with libboost 1.46 and do not break Ubuntu Precise support with system boost libraries installed.

Also, at last we are now using std::error_code and categories instead of deprecated boost::system::* analogs.
[Common] Using pure asio in benchmarks too.