Fix Alt+[0-9] buffer access order

WeeChat sends them in no particular order, we need to sort the buffers by
their WeeChat number. To avoid copying the potentially very large buffer
objects around needlessly, extract the relevant keys and sort, then access.

This is based on https://github.com/ailin-nemui/glowing-bear/commit/ad50220bfdfcf029fc47093ce5cfea04bf90fe79
Merge pull request #431 from glowing-bear/fix-buffer-ordering

Fix Alt+[0-9] buffer access order
Split things up into logical blocks
Karma: Include files in the right order

glowing-bear.js needs to be loaded before the modules building upon it
Merge pull request #430 from glowing-bear/refactor

[WIP] Refactor Glowing Bear
Create dark theme by extracting theme settings from glowingbear.css

* Remove style.css as those values should be themable as well.
* Update urls in index.html to link to dark theme by default
Provide a way to change the theme in the settings

* Selected theme is dynamically loaded
* Preferred theme is stored in the settings.
* Default theme = dark