Add support for --src-type and --dst-type

Add support for filtering by source and destination address types. Supported by
iptables only, this feature allows filtering packets by the address type (such
as whether the packet came from a local address, a broadcast address, a
multicast address, etc).

Adds the `:address_type` feature to allow a provider to declare support for
filtering on the basis of address type.
Rename {source,destination}_type to {src,dst}_type

As suggested by @dcarley.
Merge pull request #212 from alphagov/addrtype

Add support for --src-type and --dst-type
Minor fixes to appease puppet-lint

Signed-off-by: Wolf Noble <wolf@wolfspyre.com>
[#213] Improve manifest documentation

Bad me. I should have written these the first time round.
[#213] Run puppet-lint as part of CI

Will prevent lint from being violated again in the future.
Merge branch 'pr/213'

Fixes #213
Test against Puppet 3.2

Released last month.
Exclude tests for Puppet < 3.2 against ruby-head

ruby-head is currently 2.x, which Puppet only began supporting at version
3.2: http://projects.puppetlabs.com/issues/18494

This should make the "allowed failures" builds green once again.