Created a base Jinja template

...that'll be used by all our pages
Modified all pages to use our base template
Removed templating tasks from gulpfile

...as they are no longer required.
Added python files

Views have been kept in a separate folder.

This commit completes the transition of the current website to Jinja.
Ported Changelog page to Jinja

...with the help of custom jinja filters and tests.
Ported Plugins page to Jinja

After the changelog page, this one seemed really easy.
Added active nav-menu item highlight

This was the thing that made us move to jinja afterall.

Just need to set the active_page variable on every child template.
Added a custom 404 page

...which just contains a simple message now.

We could add something else later, like I'm thinking of adding a
callout by Jean Picard saying something cool.
Linux and Mac links interchanged - Fixes #8
Updated the plugins page to conform to the new json

Changes to the JSON were introduced in #6.

Beautify has been removed as that is handled by the generate_json
script.

The only thing worth noting is that the description field is assumed to
contain 'safe' html. This filed actually contains html that is used to
beautify the output in Picard's Plugin details box, but here it can be a
bit dangerous (?)
Added the API as a part of the main website (/api)