Remove whitespace generation (#5833)

* Remove whitespace generation and rely on default printing

Changes to printing:
* Add newline after last empty SwitchCase
* Add newlines around block comments if they are non-flow comments or contain newlines

* Fix a few more fixtures

packages/babel-plugin-transform-es2015-classes/test/fixtures/spec/super-reference-before-in-lambda/expected.js

@@ -7,8 +7,9 @@ var Foo = function (_Bar) {
     babelHelpers.classCallCheck(this, Foo);
 
     var t = () => babelHelpers.get(Foo.prototype.__proto__ || Object.getPrototypeOf(Foo.prototype), "test", _this).call(_this);
+
     return _this = babelHelpers.possibleConstructorReturn(this, (Foo.__proto__ || Object.getPrototypeOf(Foo)).call(this));
   }
 
   return Foo;
-}(Bar);
+}(Bar);