Allow the task "Check parameters.yml" to fail gracefully

The task "Check parameters.yml" is meant to register a variable to determine
if the task "Populate parameters.yml" should be run. So it should not
fail, but ignore any errors.
Additionally, the task "Check parameters.yml" is now set to use the .rc (returncode)
of the registered variable.
Changed all instances of "action: [module]" to "[module]:"

Discussed in #42, https://github.com/AmsterdamPHP/amsterdamphp.nl/pull/42#issuecomment-30564641
updated README to include minimum ansible version
Merge pull request #42 from ramondelafuente/feature/ansible

Allow the task "Check parameters.yml" to fail gracefully (and continue)