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
Simpler syntax for quoted cons cells
Use `rx' macro for some regular expressions
Groups on their own lines

Ideally, these groups would have explanations of what they capture.  For
now, the official stance is 'eh'.
`rx'-ify regular expression
Add some explanatory comments
Make user IDs optional when parsing from link
User IDs are very often more than one digit
Modify rx forms to be `rx-greedy-flag'-independent

See `rx' documentation for details.
Merge branch 'master' into visit-question-from-link

Conflicts:
	sx.el

Conflict arose from 6eb53ee0f12dd9f7d444e6749f6cc55c6db62078
Use string-start/-end instead of line-start/-end
Merge pull request #173 from vermiculus/visit-question-from-link

Visit question from link