Export more parts for browsers

[Flamefire]

I want to use esmangle to implement a deobfuscator in a browser.

When using the browserified version (cjsify does not work ATM) I don't get access to e.g. the common module but there are some very useful helpers (e.g. constant detection/folding)

Also exposing estraverse and escope would really help as they are already bundled, so no need to pull them in again. But due to the scoping I can't access them from outside (specifically from another script)