Fixes deprecated “signup” warning
Adds a period to the front page

The front page was (in the opinion of the author) missing a period, and
it was driving him insane, so he put it in.
Fixes naive datetimes
Updates test_front_page_sanity and test_signup for Franklin.
Adds test_crawler

This test checks all of the <a> tags on a page, and, for those with
an associated href value, follows them (note that it DOES NOT interact
with buttons).

Also adds some log files to gitignore
[Remove] Creative Commons link/icons in base.html
Changes test_crawler

test_crawler is now split into two methods, one of which returns
a list of urls, and one of which tests the urls. This is good for
modularity, and also helped fix a minor bug.
Adds pdiff crawler

Creates a new test which takes screenshots of any page it can find
and compares them to a record of what the page should look like.