[mod] upgrade versions in requirements.txt

[fix] extract_text: use html.tostring instead html_to_text.

search.py : Fix and some minor modifications

If no language is specified, bing returns results with multiple languages
for one query which isn't really useful. Setting english as default
insted if nothing.

[fix] change modal glyphicon arrows to image icons

[mod] add a search_one_request_safe function wrapper

CSS modal window for image results

Changes in search language list (continuation of #748)

that support them.
users can still query lesser supported through the :lang_code bang.

[mod] Allow users to search in most engine supported languages

Add ccctv engine to settings.yml

Online Etymology Dictionary

closes #784