[Cluster] Static cluster configuration.
[Source] Comments!
[Source] Codestyle.
[Source] More codestyle.
[Cluster] Added more diagnositics to Predefined.
[Cluster] Use `interval` argument for real.
[Source] Changelog.
[Locator] Consistent Ketama routing.

Replaced the old routing algorithm with Ketama consistent hashing one, like in Memcached. This way,
the client could provide an optional `key` argument to Locator::Resolve in order to achieve sticky
behavior, i.e. same `key` will always end up with the same version of a service, given that service
weights are not changed.
[Locator] Dropped Snapshot ID dead code.
[Cluster] Validate remote Node IDs.
[General] More const correctness.
[API] More sanity checks in Client.
[Gateway] Thread-safe Adhoc Gateway.
Merge pull request #139 from cocaine/ketama-routing

[Locator] Consistent routing.
[Locator] Do not log stuff when no RGs are there.
[Logging] Synchronizing with Blackhole v0.3.
[Logging] Fixed deprecation warnings.
[Config] Adapt config to match Logger's changes.
[Logging] Synchronizing with current Blackhole's release.