Implent getting question given answer id
Implement identifying type, id, and site of a link.
sx-open-link: command to visit links inside SX
Refactor sx-visit to sx-visit-externally
sx-open-link takes link from clipboard by default
whitespace
delay-mode-hooks on markdown-mode. Fix #159
delay-mode-hooks on code blocks
Activate major-mode when editing code-blocks
Make entire code-block a single button

This fixes a bug we had. Hitting TAB on a codeblock would move us to the
next line on the code block, instead of going to another button. Now the
entire code block is a single button, so that is fixed.
Display comment score
Support editing comments.
Fix buffer not updating after posting answers/edits.
Close compose window when buffer is killed.
Refactor comment validity checking
Do comment validity checking on edits too
Hotfix Don't use string-trim. Fix #164
Don't fill comments. Affects #141
Refactor and simplify sx-question-mode--skip-FOO functions.

They no longer need to worry about restoring point. Just move point to
its destination and return non-nil if it worked.
Don't fill headlines