Clean up and organize css properly.
Upgrade angular libs
Merge pull request #1435 from hypothesis/tags-redux

Tag Styles
Add markdown preview, add markdown help icon, and adjust styles for markdown output.
Rename icon-markdown in icomoon.css
Kill placeholder, reposition markdown icon, clean up code.
Hide comment icon when editing.
Cleaned up markdown stylings.
Added fonts.
Add onhover red to links in nav tabs.
Kill .tag-preview and add more stylings for code element.
Fixed regression where annotations weren't collapsing correctly.
Fix some problems identified by @aron.
Move css related to annotation cards to annotations.scss file.
Use tabbable directive for preview
Whitespace