Added an interop commonjs loader.
Allow module transformers to be directly passed into opts.
Merge pull request #192 from Naddiseo/function-modules

Allow module transformers to be directly passed into opts.
Merge pull request #191 from Naddiseo/commonjs-interop

Added an interop commonjs loader.
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
remove unused variable in generators/meta
revert acorn-6to5
fix bug in let scoping resulting in unneccesary replacement - closes #193, closes #185
changelog for 1.12.21