user erb to create http/https nginx config templates

By allowing user to create nginx configuration templates using ERB we have
much more flexibility. As a conclusion while adding new redirection additional
parameters can be passed, intepreted  and converted into specific nginx
configuration element inside ERB template.
redirus init generator
docs for erb templates and generator
cli options for adding properties

Add possiblity to pass location properties and options into `redirus-client`.
See `redirus-client -h` for details.
init sidekiq after setting redirus configs
mention about redirus admin responsiblities
Merge pull request #19 from dice-cyfronet/erb

Redirus should enable user to specify more configuration options for redirestions