Migrating Travis CI from legacy to container-based infrastructure

This patch should speedup testing with Travis CI using caching and
container-based infrastructure.

source:
- http://docs.travis-ci.com/user/migrating-from-legacy/
- http://docs.travis-ci.com/user/caching/

ddg encoding of URLs to UTF-8

Add Image on opensearch

some Bug fixes

[fix] Piratebay engine

Add portuguese translation

[fix] reduce server traffic by optimizing images

update dependency versions described by versions.cfg

Simply running ‘optipng’ on every PNG image reduces the overall size of
them by 10% on average.

Conflicts:
	searx/plugins/__init__.py

- regexes in a array
- regexes applied only on the last part of the url

Add a self user agent plugin

Fix vimeo

Just like with the "ip" query, duckduckgo gives the server's
information with the "user agent" query.
This corrects this behavior by adding a plugin based on self_ip.py plugin.