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.
NO-JIRA: Removed trailing whitespaces from Ruby Messenger class.
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.

Modified the Messenger class to manage instances of Selectable relating
to itself.
Test3.rb works.
Trying to fix the invalid fd state in test3.rb.