Add support for serveraliases in vhosts

These vhost shorthands don't currently support setting serveraliases, which the
underlying nginx::vhost does. Allow use of serveraliases in vhost::* by adding a
default parameter to each.
Merge pull request #5 from alphagov/vhost-serveraliases

Add support for serveraliases in vhosts
Fixing declaration bug, setting caches to default to an empty array.

https://jira.puppetlabs.com/browse/ops-1008
Merge pull request #7 from puppetlabs-operations/ops_1008

Fixing declaration bug, setting caches to default to an empty array.
Decouple from Puppet Labs

This code allows the nginx module to be used outside of the Puppet Labs
environment. It also updates templates to use the new method of
accessing variables.
make sure we have some defaults for ssl