[WIP] Big Restructuring: Embedded AST

Now espower embeds target AST substree and tokens into output, and using subpath notation to point them.

* [x] Re-Design
* [x] Spike
* [x] Add esprima to runtime dependencies
* [x] Drop CoffeeScriptRedux support for now
* [x] Rough implementation
* [x] Maint tests
* [x] Drop location adjusting
* [ ] Move position adjusting logic to power-assert-formatter
* [x] Delete unused tests