* 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
* moved applying arguments inside new Promise handler block
* updated test fixture to reflect change
* corrected the apply to use correct scope and arguments
* added regression test for issue #4943, added async-to-generator/async-default-arguments test
* added regression test for issue #4943
* switched back to using arrow function, since now pointing to v7 release base branch
* simplified async-to-generator regression test for issue #4943, imrproved change to self/arguments refs by using arrow function on returned promise
* updated text fixtures
* removed es2015 preset usage from issue #4943 regression exec test
* added use strict to test fixture
* added use strict to test fixture
* added destructing transform to test options
* removed use strict from exec test
* added parameters & destructing transforms to test
