Changing rosinstall URI's to HTTPS (no SSH keys)

This change will allow users to use wstool to download and install
the Baxter SDK without having to setup SSH keys with Github.

* Note that users will still need to go through the ssh key setup
  process if they want to clone private repos, like the gazebo sim.
Merge pull request #159 from RethinkRobotics/https_rosinstall

Changing rosinstall URI's to HTTPS (no SSH keys)