move to php-http/httplug

• moved http library to php-http/httplug (instead of egoleon/http-adapter)
• dropped 5.4 support
• fixed minor bug in docblock parsing

Migration of the HTTP-Layer (only needed if you dont use the phar)

since we are relying on php-http we dont ship a default http implementation (for dev we do).

install Puli on your System first:

$ curl https://puli.io/installer | php

choose one of these Client Adapters and require it with composer. e.g. :

$ composer require php-http/guzzle6-adapter

and your done!