unworking, direct copy of BIP 32 implementation

This BIP 32, or HD wallet implementation is directly copied from this repo:

https://github.com/sarchar/brainwallet.github.com/tree/bip32

It does not actually work with this commit, since it is designed to work with
bitcoin-js in the browser. It needs to be modified to work with bitcore in node
and the browser.
update version to 0.1.8

Changes since version 0.1.7
* Refactor browser building
* Examples of signing transactions
* Key interface is now bitcore.Key, not bitcore.KeyModule.Key
** bitcore.KeyModule is deprecated
* Bug fixes
Merge pull request #164 from ryanxcharles/feature/npm-0.1.8

update version to 0.1.8