New catalogue

This is a major change merging from the `catalogue` branch, which I have been working on for several weeks now.

The biggest change is the new catalogue (`/fonts` page) and its features, as well as a completely new way of organizing font metadata.

The new catalogue allows users to click through to individual font specimen/test pages, as well as to add fonts to their "bucket", and have the site generate the appropriate `link` tag to go in their website's source code. The specimen pages use the Brick fonts directly, giving users an accurate representation of how the font will look and render in the browser. The pages are also `contenteditable`, which allows for users to type in custom content to test.

We accomplish this through the use of a Jekyll collection. Each font's metadata is placed strategically in the front-matter of an `index.html` page in the `_fonts/[font-name]` directory. This allows us to generate the specimen pages for each font while being able to access the list of fonts and their metadata with only one metadata source.

Of course, these substantial changes require rewriting parts of the [Contributing](https://github.com/alfredxing/brick/wiki/Contributing) wiki page, which I will do later.

Most importantly, please test out the new site and any of your sites that are using Brick, to make sure that I didn't miss any bugs.

:octocat: