First 5.0 working release

Breaking changes:

• whole API is using async/await instead of callbacks
• drivers was moved to separate packages

Babel 6 and Travis

• upgraded to babel6
• travis testing for node 4, 5 and iojs
• refactored tests and added tests for getScope
• changed importing to:

import RBAC, { Role, Permission, Storage, Memory, Mongoose } from 'rbac';

if you are using ES5 please use default

var RBAC = require('RBAC').default;
var Role = require('RBAC').Role;

3.1.2

Fixed bug in the mongoose storage engine.
Please use this version if you are using mongoose.
Thank you @yaomingdan