Modernize module

Taking a quick pass at adding support for Travis, Puppet v3, Ruby 1.8.7,
1.9.3, and 2.0.0 and passing lint. Also specifies the version of concat
(1.1.0) and stdlib (4.1.0).
This line still needs fixing https://github.com/puppetlabs/puppetlabs-dhcp/blob/2a4709c36c9179a84ed63a54c138643e340df192/templates/dhcpd.conf-header.erb#L13