* Slightly simplify logic
* Implement ES2016 check for simple parameter list in strict mode
See e.g. ECMA-262 7.0 14.1.2:
> It is a Syntax Error if ContainsUseStrict of FunctionBody is true and
> IsSimpleParameterList of FormalParameters is false.
Similar clauses cover arrow functions, generator functions, methods, and
generator methods, as well as async functions and async arrow functions.
I'm extremely stupid and didn't commit as I go. To anyone reading this
I'm extremely sorry. A lot of these changes are very broad and I plan on
releasing Babel 6.0.0 today live on stage at Ember Camp London so I'm
afraid I couldn't wait. If you're ever in London I'll buy you a beer
(or assorted beverage!) to make up for it, also I'll kiss your feet and
give you a back massage, maybe.
