Updated to work with Vert.x 2.1M2

Forked from 2.0.1-final (not including latests changes for Vert.x 2.1M3). 
This changes allows to use the Maven plugin with Vert.x 2.1M2. 
Current plugin version (2.0.1-final) uses 2.1M1 and if the project uses 2.1M2 it throws errors on execution (classes not found: CaseInsensitiveMultiMap for example)