NO-JIRA: Added a means for providing method hooks to the Ruby bindings.

The new module, Filters, mimics the functionality of the Ruby On Rails
filter system.
PROTON-531: Expose the passive mode in Ruby bindings.

Added the mutator methods to Messenger. Updated the Rspec tests to
verify the changes.
PROTON-531: Created the Selectable class for Ruby.

The class encapsulates the underlying file descriptors used by Messenger
when in passive mode.