Port CSS away from Bootstrap

[DangerOnTheRanger]

This PR fixes #163 by removing any dependency on Bootstrap and some associated stuff like JQuery. In terms of design, the aim is to keep Maniwani with roughly the same look as before, but with some modifications made to distance the project from Bootstrap a bit. For instance, this is what viewing a thread on the ported stock theme looks like as of the first commit in the PR:

The remaining work before this can be merged is:

• [x] Port the harajuku theme, re-examine the color palette to come up with something a little more cohesive and easier on the eyes
• [x] Port the wildride theme
• [x] Add a new Tomorrow-based theme (call it 明日/Ashita perhaps?)
• [ ] Style moderation tools/dropdown
• [ ] Add mobile navbar

[DangerOnTheRanger]

For the stock theme, I inverted the colors for foreground and background, so now everything is white-on-gray instead of gray-on-white. Should add a little bit of contrast to posts.

This is how the white-on-gray looks for the catalog/firehose, by the way.

[DangerOnTheRanger]

Same thread with the new/work-in-progress Ashita theme:

[DangerOnTheRanger]

And the slightly-touched-up harajuku:

[DangerOnTheRanger]

And wildride is brought bootstrap-less and up to date: