Add purposeful failure test to examine travis build

.travis.yml

@@ -11,6 +11,7 @@ install:
 
 script:
     - npm run lint
+    - npm test
 after_script:
     - npm run coveralls
 

spec/rules-spec.js

@@ -1,4 +1,4 @@
-/*global describe, it, expect, beforeAll*/
+/*global describe, it, expect, beforeAll, fail*/
 
 const Sym   = require('../lib/rules').Sym;
 const Rule  = require('../lib/rules').Rule;
@@ -85,5 +85,7 @@ describe('Rule', () => {
     expect(filteredRhs.length).toBe(3);
   });
 
+  it('force fail', () => fail());
+
 });