added CONTRIBUTING.md
added CONTRIBUTING.md

nsivraj/arewefamily,Itaqua/vertx-mod-asterix,bisrael8191/vertx-mod-persona,nsivraj/arewefamily,unSinn/vertx-mongo,unSinn/vertx-mongo,unixunion/vertx3-gradle-template,tstout/vert-x-learning,muraken720/vertx-test-example,grimrose/vertx-polyglot-sample,sendgridlabs/vertx-scheduler,Itaqua/vertx-mod-asterisx,it-nalon/jmusic,tstout/vert-x-learning,unSinn/vertx-mongo,sendgridlabs/vertx-scheduler,yaykuy/vertx-loader,unixunion/transponder,bisrael8191/vertx-mod-persona,unixunion/transponder,unixunion/deblox-vertx-template,nsivraj/arewefamily,unixunion/transponder,unixunion/deblox-vertx-template,grimrose/vertx-polyglot-sample,grimrose/vertx-polyglot-sample,tstout/vert-x-learning,nsivraj/arewefamily,unixunion/deblox-vertx-template,muraken720/vertx-test-example,unixunion/transponder,monoid-us/vertx-postgresql,sendgridlabs/vertx-scheduler,it-nalon/jmusic,Itaqua/vertx-mod-asterix,unixunion/transponder,nsivraj/arewefamily,tstout/vert-x-learning,it-nalon/jmusic,tstout/vert-x-learning,it-nalon/jmusic,unSinn/vertx-mongo,grimrose/vertx-polyglot-sample,sendgridlabs/vertx-scheduler