fix many test problems (#1677)

* fix many test problems

- adds [stoppable](https://npm.im/stoppable) to force-stop net & http
  servers
- upgrades to latest mocha
- much cleanup of servers
- some removal of useless code

Signed-off-by: Christopher Hiller <boneskull@boneskull.com>

* increase wait time to hack at race condition

* PoC with fork of stoppable

Signed-off-by: Christopher Hiller <boneskull@boneskull.com>

* fix custom stoppable url for newer npm

* make travis go faster; attempt to avoid npm troubles

* fix coveralls executable path

* add extra time for flake to trigger spec

Signed-off-by: Christopher Hiller <boneskull@boneskull.com>

test/nodes/core/logic/15-change_spec.js

@@ -578,7 +578,6 @@ describe('change Node', function() {
         });
 
         it('reports invalid regex', function(done) {
-            var sinon = require('sinon');
             var flow = [{"id":"changeNode1","type":"change","action":"change","property":"payload","from":"\\+**+","to":"NUMBER","reg":true,"name":"changeNode","wires":[["helperNode1"]]},
                         {id:"helperNode1", type:"helper", wires:[]}];
             helper.load(changeNode, flow, function() {