Pull output functions out to module

These functions will want to be shared between any future commands so it
seemed prudent to pull them out to a module that can be shared.
Ignore build and dist dirs
Long description should be read from README.rst
Add check_apt_security_updates command

Checks that the number of security patches waiting to be applied are
within the given bounds.

Adapted from a bash script of the same name from GOV.UK puppet.
Bump version to 1.1.0

We have added some new functionality so bump the minor number
Merge pull request #1 from alphagov/check-apt

Check apt