fixed automatic comma insertion cf #950
PR rebased. tests passed.
added A LOT of tests
renamed isMozOrESNext to isAfterESNext;
refactored ESnext/Moz support to raise errors on future features;
fixed several parsing issues
Signed-off-by: Bernard `Guyzmo` Pratz <email@example.com>
updated automatic comma insertion support (cf #950)
added line breaking error on 'return' statement with and without asi …
…option (when it's broken, fix it).