In order to use another cache tool or to use spot without cache
system.

With SEARX_LOGGER setting we can run spot with
the expected logger level.

pep8 is deprecated, it is replaced by pycodestyle.

In order to run the project in a dedicated environment this
patch introduces the docker-compose file. To join redis service
a setup via an environment variable `SEARX_REDIS_HOST` is added.

To avoid to wait 10s when we stop the spot container, this
patch performs some changes to only run the python binary in the container.
Tini is included in docker itself since 1.13 or greater, so it is removed
and the environments variables are handled in the application, that change avoids
to use a bash script to patch the configuration.

Related to discussion in #1124
The io.open import is necessary for python2

SearX currently doesn't start up when run with Python 3 as it tries to parse the
settings.yml file with ASCII codecs.
There are similar problems with engines_languages.json and currencies.json
Python 3 requires that files with Unicode characters be read with a 'b' flag.
This also works with Python 2 and hence can be integrated into the main source
code.

Tested with the latest Python 3.6.4rc1 on Debian unstable.
Signed-off-by: Joseph Nuthalapati <njoseph@thoughtworks.com>

The exact order is
* first from SEARX_SETTINGS_PATH,
* if not found then from searx code base,
* if not found then from /etc/searx/settings.yml
* if not found an exception stops searx loading

* parsing XML-Files which contain target, exclusions and rules
* convert regex if required (is a little hack, probably does not work
for all rules)
* check if target rule apply for http url, and use the rules to rewrite
it
* add pice of code, to check if domain name has not changed during
rewrite (should be rewritten, using publicsuffix instead of little hack)

* add comments
* add licence-header