Add bare bones `localExpand`

This is a simple implementation of local expansion. It currently does
not support stop lists, but fully expands the syntax given to it.
allow yield* as a unary operator (fixes #372)
final camera ready
back to preprint
Fix empty trailing macroclass in delimiters

Fixes bug brought up in #384
Merge pull request #391 from natefaubion/trailing-macroclass

Fix empty trailing macroclass in delimiters
debug.js now works out of the box
removing contracts from the browser scripts
Merge branch 'master' of github.com:mozilla/sweet.js
fixes typo, rebuilds docs

This PR corrects builtin --> built-in typo. It also runs
`grunt docs` for building again the documentation.
build docs
adding a test for generators
build
Merge branch 'pr/373'
disabling contracts
build
use default readtable for stxcase.js
build
fix custom operators as LHS of assignment
build