Improve installation directions (python#1410)

Mention 'vagrant up' and activating virtual environment in
the 'next time' section.

Author: eamanu

docs/source/install.rst

@@ -41,10 +41,13 @@ Now use your favorite browser to go to http://localhost:8001/. The admin pages
 can be found at http://localhost:8001/admin/. You can use your superuser
 credentials to log in to Django admin.
 
-You will only need to run the following two commands the next time you want to
+You will only need to run the following five commands the next time you want to
 work on python.org::
 
+    $ vagrant up
     $ vagrant ssh
+    $ cd ~/pythondotorg
+    $ . venv/bin/activate
     $ ./manage.py runserver 0.0.0.0:8000
 
 .. _Vagrant: https://www.vagrantup.com/downloads.html