Allow greater flexibility in listen directive.

Currently the module does not allow to specify specific bind options
per IP we are binding haproxy onto.
Hence, if a user has a service available across several network, but
with different haproxy bind option according to the network, s/he can't
configure haproxy with the current state of this module.

It aims to make it possible to have configuration as the following:

  bind 192.168.2.1:80 ssl crt public.puppetlabs.com.crt
  bind 10.0.0.1:80 ssl crt private.puppetlabs.com.crt
  bind 178.35.67.12:80
Merge pull request #119 from Spredzy/more_listen_flexibility

Allow greater flexibility in listen directive.