Make node --harmony bin/cake test pass on Node 9 (#5012)

* Make `node --harmony bin/cake test` pass on Node 9

Make classMaker() explicitly return an object

* Update Travis and AppVeyor to use --harmony and v9

.travis.yml

@@ -3,6 +3,7 @@ language: node_js
 node_js:
   - 6
   - 8
+  - 9
 
 cache:
   directories:
@@ -14,5 +15,6 @@ script:
   - node ./bin/cake build:full
   - node ./bin/cake build:browser
   - node ./bin/cake test
+  - node --harmony ./bin/cake test
   - node ./bin/cake test:browser
   - node ./bin/cake test:integrations

appveyor.yml

@@ -2,6 +2,7 @@ environment:
   matrix:
     - nodejs_version: '6'
     - nodejs_version: '8'
+    - nodejs_version: '9'
     - nodejs_version: '' # Installs latest.
 
 install:
@@ -19,6 +20,7 @@ test_script:
   - node ./bin/cake build:full
   - node ./bin/cake build:browser
   - node ./bin/cake test
+  - node --harmony ./bin/cake test
   - node ./bin/cake test:browser
   - node ./bin/cake test:integrations
 

test/classes.coffee

@@ -266,6 +266,7 @@ test "classes with value'd constructors", ->
     inner = ++counter
     ->
       @value = inner
+      @
 
   class One
     constructor: classMaker()