more regenerator spring cleaning
add assertion checks into types
add util.arrayify and util.regexify
use regexify and arrayify in register options
expose util as _util
arrayify whitelist and blacklist, inherit moduleRoot from sourceRoot and vice versa
check for existence of node before checking it in let scoping
clean up common-interop module formatter
use commonInterop module formatter in 6to5/register
generator: add existence check to printJoin
add interop-require declaration
publish acorn-6to5 as an npm package - fixes #187