Add bitters stylesheets.

Rename some files to .scss for easier import.
Split up _base into two files.
Convert all sass to scss.
Make form behave like before.
Add link to "logo".
Add item list link to header.

Extract text-link styling into mixin.
Change some double quotes to single quotes.
Tweak some padding.
Change H2 in search results to H1.
Make button text a bit bigger.
Make hovered over items slightly darker.
Merge branch 'prettier_design'