* Return inserted/replaced paths
This gives `Path`’s replacement and insertion methods a consistent
return value: the inserted/replaced paths.
Before, they could return `undefined`, a `node`, or a the current path
inside an array. It was kinda pointless. But now they always return an
array of paths, which is useful for solving
https://github.com/babel/babel/pull/4935#discussion_r96151368.
* Return inserted nodes and not BlockStatement
Addded test for bug #4363
* Cleanups
- `#replaceWith` will now return the current path if it's the same node
- `#insertAfter` and `#insertBefore` use public Path APIs now
- Makes container insertion faster (single splice call)
- Use public APIs in container insertion
- Replacing a statement with an expression returns the expression's path
- Replacing an expression with multiple statements returns the inserted
closure's body's paths.
* Handle arrow function processing via shared API rather than default plugin.
* Fix a few small PR comments.
* Preserve existing spec arrow 'this' rewrites, and support spec in subclass constructors.
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.
