Strict option to fix #174.

[wbyoung]

This is a backwards-compatible fix for #174 that would probably be preferable over #320. It requires passing options to, exports({ strict: true }) to ensure no conflicting methods get added to lodash / underscore.

I think this seems like a good way of handling things, and the strict option could be documented such that it will always maintain compatibility with any enhancements added to lodash / underscore. For instance, if count was added to either, underscore.string would be updated to not export it (possibly causing some applications to require updates).