New installation document.
Actual script that installs flocker, and demonstrate how to use
flocker-deploy after installation.
Explain how to run the script.
Link to issue to switch to real URL, and switch to a URL that will work for now for testing purposes.
Address review comment: Remove reference to piping curl to shell.
Address review comment: more portable way of setting $PATH.
Address review comment: no need to install python-pip.
Address review comments: Documentation tweaks.
Address review comment: Explain why we need newer pip.
Address review comment: More documentation links in README.
Merge pull request #349 from ClusterHQ/ubuntu-install-86

Ubuntu install documentation.

Fixes #86.