Re-enable solidity coverage

- Upgrade version
- Re-enable in travis.yml
- Move mocks to contracts folder for instrumentation

test/RBAC.test.js

@@ -1,7 +1,7 @@
 import expectThrow from './helpers/expectThrow';
 import expectEvent from './helpers/expectEvent';
 
-const RBACMock = artifacts.require('./mocks/RBACMock.sol');
+const RBACMock = artifacts.require('mocks/RBACMock.sol');
 
 require('chai')
   .use(require('chai-as-promised'))