* Added a parameter to lambertw allowing you to calculate the non-principal branch
* Changed all cases where a constant or parameter is returned directly, to reduce the likelihood of accidental mutation
* Changed how tetration for bases <= e^1/e works: now the property x^^(n + 1) == x^(x^^n) always holds, and small bases with large payloads behave correctly.

…ty.js

As described in #162

This one's a breaking change, so I guess we're on v2.0.0 now!