Fix connection timeout

[ztanis]

• fix connection and read timeout. Expected behaviour is that connection timeout is 10 seconds. But really it was still 60 seconds. The reason is that Net::Http.start method starts connection with default current timeouts and than applies passed block.
• allow to configure connection_timeout and read_timeout.
• fix outdated usage examples in README (Very basic documentation issues, and possibly a bug. ruby-druid/ruby-druid#7).
• add example of connection to static host rather than using zookeeper service discovery.