Update Readme with Maven/Gradle install instructions
Update Readme with Maven/Gradle install instructions

Just like described in here: https://groups.google.com/forum/#!topic/vertx/hLX3jM9cpgA
khasinski/mod-lang-php,khasinski/mod-lang-php,khasinski/mod-lang-php,alwinmark/vertx-php,vert-x/mod-lang-php,vert-x/mod-lang-php,alwinmark/vertx-php