Documentation -- part one

Pushing this change to continue work elsewhere.
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
Minor typos and incorrect information
Remove -cache-p
Enhance documentation
Provide alias for `sx-auth-authenticate'
Follow package.el convention
Use `user-error' when there's no question at point
GitHub comments -- #77
Reflect new purpose of sx.org
Merge pull request #77 from vermiculus/documentation

Documentation