Identify ourselves with an "User-Agent" header.
Change request path in bad input test.

Change the request path used in the bad input test, as previously the
request URL would end up being "https://api.nearlyfreespeech.netDERP"
which could cause issues (for instance, OpenDNS's typo-correction
feature would make "run_request" return the source of a page of search
results instead of failing).
Add licensing junk to the readme.