Upgrade to our own libreoffice module

- jasonamyers/puppet-libreoffice doesn't work as it refers to a download
  that doesn't exist.
- boxen/puppet-libreoffice doesn't allow installation of other versions
  and still doesn't work as it refers to a different download that
  doesn't exist

I forked the module, parameterised the version and switched our Boxen
installation to use that.
[samjsharpe] Become standards compliant
Merge pull request #67 from alphagov/update-libreoffice

Upgrade to our own libreoffice module