Simplify Vagrant and Ansible file

Speedup: Remove installation of latest Ansible with PPA. Made provisioning
compatible with older Ansible versions from the Ubuntu repositories.
Simplify: Vagrant files. Remove different groups which are not used.
Vagrant also does not support options. Better put production based Ansible
provisioning in a seperate repo. Vagrant should be only used for local dev
instances and is not a good solution for real server provisioning.
Remove also group vars.
add note regarding virtualenv
Merge pull request #959 from PyBossa/issue-simplify-vagrant-ansible

Issue simplify vagrant ansible