Many improvements

  * Set default devstack to master
  * Proxy URLs now must have an explicit scheme. A MissingSchema
    exception will be raised if they don't.
    https://pypi.python.org/pypi/requests
  * Add a 0 timeout for aptitude module
  * Update install_devstack.sh.erb to:
    - Create the vms-talk.sh script to enable clients to talk with outside
      world in ~/home/vagrant
    - Add trove support