Test improvements.
Code improvements.
Move specs into appropriate subdirectories.
Namespace specs appropriately.
Fix tests where we couldn't run binary after running in-memory.

We never uninstalled our signal handlers, so running rflow from Open3 always triggered SIGCHLD, which triggered a shutdown.
Caller should be logging exceptions, instead of logging at the callsite.
Remove unused code.
Refactor rflow.rb.
Refactor rflow/master.rb and create DaemonProcess.
Refactor rflow/shard.rb and create ChildProcess.
Refactor rflow/component.rb.
Refactor rflow/components/raw.rb.
Refactor rflow/component/port.rb.
Refactor rflow/connection.rb.
Refactor rflow/connections/zmq_connection.rb.
Refactor rflow/logger.rb.
Refactor rflow/message.rb.
Refactor rflow/pid_file.rb.
Refactor rflow/configuration.rb.
Refactor rflow/configuration/* except for ruby_dsl.