Add the `mirror` option and verify if a package is already installed.
Add the `mirror` option and verify if a package is already installed.

By default, the cpanm client will use a default mirror to download
libraries, but it's possible for the end user to pass a different URL.

Since ansible favorite idempotence when possible, we verify if the
module is already installed before running the cpanm client.

Another minor additional change, the `notest` option is now a boolean.

thaim/ansible,thaim/ansible