[fix] Display multiple answers in wolframalpha_api

The answer is scraped from a js function, so parsing the html tree
doesn't achieve anything here.

[fix] #471 #463 fix old openssl(<1.0.2) requests verify error

Wolfram Alpha API

forfuckssaketravisnotagain

More appropriate in this case because it will always give just one
answer.

[enh] improve gigablast engine

nid/pref cookies are also removed

Update OpenSearch Description

btdigg engine: fix text mojibake.

Don't throw away the request if pageno is wrong

Update settings.yml

fix: update buildout

This fix the test failures related to 01d2fb9f703fee2a28cdb4c6583158054f9d7558