Squashed '.themes/whitespace/' changes from 67b9c87..f41aafb

f41aafb Merge pull request #39 from yous/patch-external-url
ba3bbe4 redefined white as white (cream doesn't cut it for our theme)
78f920a Modified notice about what belongs in this file
445bac1 Avoid adding styles to `custom` directory
b533039 Add External URL section
3515071 Use `$text-color` for color of title link and visited title link
72b4ba2 Add right arrow at the end of title when the post has `external-url`

git-subtree-dir: .themes/whitespace
git-subtree-split: f41aafb5dcb78c374fa5d81dfa93f7aa17a58cbe
Merge commit 'd02704cfffcb95988089ff2a61cfc9d01a99f11b' into source
Apply whitespace theme
Make `<br>` tag by adding two spaces at the end of line
Replace `&#39;` with `'` except for special cases