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.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1588958 13f79535-47bb-0310-9956-ffa450edef68
NO-JIRA: Removed trailing whitespaces from Ruby Messenger class.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1588959 13f79535-47bb-0310-9956-ffa450edef68
PROTON-531: Expose the passive mode in Ruby bindings.

Added the mutator methods to Messenger. Updated the Rspec tests to
verify the changes.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1588960 13f79535-47bb-0310-9956-ffa450edef68
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.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1588961 13f79535-47bb-0310-9956-ffa450edef68
PROTON-531: Ruby example - passive_recv.rb

The example uses passive mode to demonstrate how to write non-blocking
code in Ruby.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1588962 13f79535-47bb-0310-9956-ffa450edef68