Various fixes in Chapter 11

Hello again,

Sorry for the long break between this and the last PR.

This PR includes all the things I could see in Chapter 11. The following is a list of the changes I made:
* Fixed indentation errors throughout. I hope I didn't screw things up in the process.
* Fixed various space (missing and extra) issues
* Fixed a couple of typos
* Added the ``{% load static %}`` to ``base.html`` so Django doesn't get angry
* Changed all ``<input>`` tags to ``<button>`` tags because that's what we did when we first switched to Bootstrap.
* Closed a forgotten ``<p>`` tag.
* Changed all ``<br/>`` tags to ``<br />``

I definitely hope that I didn't screw up the .rst file, if I did, please let me know so I can fix it and send in another PR.

Cheers!