[FIX] odoo-shippable: Solve issues after dropped support of Python3.3

This applies the following fixes, mostly related to issues due to dropped support for Python3.3:

• Freeze virtualenv version: Starting from version 16.0, virtualenv is not compatible with Python 3.3 anymore. Therefore, the virtualenv version needs to be freezed for that Python version.
• Don't install virtualenv twice: virtualenv was being installed again when creating environments for all Python versions
• Print messages when installing pip for all versions
• Fix small typos in messages printed when creating virtualenvironments
• Add a missing $ character in the library (my bad)
• Remove redundant parameter -p when creating virtualenvs
• Install all Odoo versions from Vauxoo and Odoo; V11 was not being installed

Closes #309 (closed)