buffer upgrades

[calvinmetcalf]

seems like we're going to need to upgrade bn.js to deal with buffer depreciations see browserify/publicEncrypt#20 browserify/createECDH#13 browserify/browserify-sign#45 and browserify/diffie-hellman#31# which will all need to be upgraded in sync in order to make sure they all use the same major version of bn one

[fanatid]

Initial issue in elliptic repo: indutny/elliptic#191

[rawr51919]

This should be fixed in #200 because we switched to Buffer.from() there, but I'd like input on this. The others can also be easily fixed, or are already fixed. The only thing keeping all these from being officially fixed is for browserify/diffie-hellman#31 to have bn.js updated. May be thinking of superseding it due to inactivity though.

[rawr51919]

A dependency updater like Depfu would be nice to have to keep dependencies like bn.js updated so that way we don't have to worry about keeping them in sync, because that'll do it for us. It's probably something for another issue, though