Formatting: remove white space
Revert "Fixed: replace improper nested selectors"

This reverts commit 9f1a1129113aba25ea852b4f32636be7f073b48d.
Fixed: diva.destroy() deletes highlights data, canvas localStorage

Added destroy() methods to canvas and highlight plugins.

Refs #198
Docs: remove old argument

This argument doesn't exist anymore, since we're using events instead of callbacks.
Revert: don't delete canvas settings from localStorage on destroy

Reverts part of 2a3a1ca8d70a9d819e11af46f37f5dad25f04b3a
Fixed: redundant button CSS

Previously, the LESS stylesheet was generating CSS for buttons using mixins, meaning that the generated stylesheet included many repeated styles. Now, we just create a single 'button' class inside mixins.less and apply it using the 'class' attribute of the HTML tags. This means the 'button' chunk of CSS now only gets loaded once, instead of for each button that uses it.
Fixed: scrolling in fullscreen grid view breaking toolbar layout

Fixes a bug wherein scrolling in fullscreen mode when in grid view moved the (+/-) buttons down. This was happening because the digits were expanding the width of the right toolbar container, pushing the buttons label down.
Fixed: both zoom labels ('zoom level' and 'pages per row') appearing in fullscreen mode

CSS fix in 846b6ae4266349e8d362b43dc6957c189cc8ee8e introduced this bug, wherein both labels appear upon initial load in fullscreen. Bugfix works as initially intended without this line.
Merge branch 'develop' of https://github.com/ddmal/diva.js into horiz-scrolling

Conflicts:
	source/js/diva.js