Add a install-deps script

A script to install dependencies needed to run the test suite.
Rename the setup script to setup-virtualenv
ADd the --enable-tests options

An option to only run some selected tests.
Add https-everywhere tests

Add a first test that check that https-everywhere is enabled, and that
loading a http URL redirect us to the https URL.

A second test is checking that the same http URL is not redirected to
a https one when the https-everywhere addon is disabled.