Update mocha version & fix should.be API use error.

A mocha defect silently ignored this for the previous package-lock mocha
version (5.0.1).

See the following issue and changelog:

mochajs/mocha#3226
https://github.com/mochajs/mocha/blob/master/CHANGELOG.md#502--2018-03-05

Test should have failed in all cases, but false passing occured with older
mocha versions.

Author: jleverenz

package-lock.json

@@ -29,7 +29,7 @@
   },
   "devDependencies": {
     "coffee-script": ">= 1.8.0",
-    "mocha": "^5.0.1",
+    "mocha": "^5.2.0",
     "request": ">= 2.9.203",
     "should": "^13.2.1",
     "sinon": "^1.17.4"

package.json

@@ -154,7 +154,7 @@ describe 'livereload server startup', ->
   it 'should gracefully handle something running on the same port', (done) ->
     new_server = livereload.createServer({debug: true, port: 35729})
     new_server.on 'error', (err) ->
-      err.code.should.be("EADDRINUSE")
+      err.code.should.be.equal("EADDRINUSE")
 
     done()