Add Nginx support

First draft for doc and the basic conf

Nginx class now extends AbstractCacheProxy #34 - Added purging test for different location setup

Fixing Scrutinizer issue

Update NginxTestCase.php

Refresh method and test

Removed empty line

Few more CS fix

Added nginx as keyword

Added nginx to Travis

Added HTTPS

Typo

Removed empty line

added nginx installation script on travis before_script

Nginx custom build script

Few fix for nginx installation process

Correct path

Correct path

Merging classes Sperate/Same Location

Removed useless config directives

All NGINX files are now set to /tmp

Set more NGINX conf to /tmp/

Install custom NGINX the other way

Update install-nginx.sh

Fixing permissions

New method addRiskyTest required for phpunit >= 4

Installation is needed

Add shebang

Remove NginxSeparateLocation

Also support same location
Improve docs

Add links to Nginx docs
Fix CS
Add shebang