Footer is sticky-ified

Here are the code changes to get the footer sticky.  Here's how I did this:

I "inspected element" for the flixter that we have up in heroku and went through the elements that were different and made the HTML match exactly the same.  Then I stole the CSS from the flixter app I had.  Here are the changes that I needed to make.
First I put all the footer specific stuff into a separate css file, `footer.css.scss`.