Prune unused parameter
Add missing dot-operator
Augment `sx--thing-as-string' to hexify as needed

Also fix issue where function options would not be transferred from the
original use into its recursive steps.
Hexify value in key-value pairs

Fixes #130
Add tests for `sx--thing-as-string'
Merge branch 'master' into issue-130

Conflicts:
	sx-request.el

Conflict was trivial.
Merge pull request #131 from vermiculus/issue-130

url-hexify values in key-value pairs