[TEST] Adds tests for reopening classes (#180)

Author: Chris Garrett

transforms/ember-object/__testfixtures__/class-reopen.input.js

@@ -0,0 +1,7 @@
+import EmberObject from '@ember/object';
+
+const Foo = EmberObject.extend({});
+
+Foo.reopenClass({});
+
+export default Foo;

transforms/ember-object/__testfixtures__/class-reopen.output.js

@@ -0,0 +1,9 @@
+import classic from 'ember-classic-decorator';
+import EmberObject from '@ember/object';
+
+@classic
+class Foo extends EmberObject {}
+
+Foo.reopenClass({});
+
+export default Foo;