Update to newest Multiverse-Core version

Update from 2.4 to 2.5 multiverse-core version
Check your ide , the lib change can break your build

The API provide a function to get the generator

Xephi
Check MultiverseCore version
Suround with try clause for more security
Create Readme
Update README.md
Merge pull request #19 from Xephi/master

Updated to latest Multiverse-Core version, added ReadMe