Documentation -- part one

Pushing this change to continue work elsewhere.
Define sorted insertion macro.
Implement hidden question database

Also improve read question code.
Hidden question functionality implemented in the question list
Merge branch 'master' into hidden-questions
Implements indication of starred questions in question-list

`sx-question-list-favorite` inherits face from
`sx-question-list-score-upvoted`

Favorite is displayed using char \x2b26 WHITE MEDIUM DIAMOND.
Merge pull request #72 from jleechpe/sx-questions-show-favorite

Implements indication of starred questions in question-list
QUICK-FIX: Link regexp Fixes #74
Merge pull request #73 from jleechpe/invalidate-cache

Provide cache invalidation
Merge pull request #71 from vermiculus/hidden-questions

Hidden questions
Mark as read with "m"

Fixes #61
Merge pull request #76 from vermiculus/mark-read-key

Mark as read with "m"
Add some package definitions.

Also run checkdoc on sx.el
Fix missing dependency
Documentation -- part two

Pushing this change to continue work elsewhere.
Simplify `sx-method-call'

We aren't using `stack-filter' anymore (in fact, we haven't since
filters became functional).  Somehow it survived refactoring; this
commit fixes that oversight.
Documentation -- part three

Source code is documented to the best of my knowledge and understanding.
Update user manual

Removed developer reference since this should be embedded in docstrings
for the most part.
Merge branch 'master' into documentation

Conflicts:
	sx-method.el
	sx-question-list.el
	sx-question-mode.el
	sx-question.el
	sx-request.el
	sx.el
Add `customize' data