Support u flag for regular expressions

[mathiasbynens]

See https://mathiasbynens.be/notes/es6-unicode-regex for more info on this feature.

Here’s a module you can use for the transpilation: https://github.com/mathiasbynens/regexpu Traceur and 6to5 Babel depend on regexpu as well.

[mathiasbynens]

There is now a separate module for just the regular expression rewriting logic: https://github.com/mathiasbynens/regexpu-core