Allow users to change their password
Merge remote-tracking branch 'gray/change-password' into change-password
moved password changing to the UserController. Also extended the
form to require the current password in order to change, as well as
repeating the new password. Added @author note to UserController that
the changePassword action is based on work from someone else.

Closes #108, #107
updated Linux installation instructions

Since Ubuntu 12.04 ships with PHP 5.3 it is no longer supported. The instructions are now geared toward Wheezy and Ubuntu 14.04 or newer. Closes #106.