flattening tail spread recursion

[lightmare]

Q	A
Fixed Issues?
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

edit: Perhaps important to note that I changed not just the implementation, but also some semantics. In particular, I wrap every expression in the list in an arrow function. Which has several effects:

// previously, this referred to the generator expression object,
let genMember = *[this.foo]; // lexical this with this PR

// previously, yield was allowed but produced really strange behaviour
let genYield = *[yield 5]; // illegal with this PR

[MaxMotovilov]

Really ingenious solution with some extra overhead that can be partially undone with further refinement.