Added alternative cryptocurrency chooser

Added cryptocurrency chooser to the interface. This allows a user to select different crytpo-currencies and create pub/priv keys for any of them.

![cryptocurrency chooser](https://f.cloud.github.com/assets/116830/2181804/d0478542-9767-11e3-997a-b2150b29f49a.png)

The chooser has a search box for quick filtering down the currency the user is looking for.

This requires the latest [pull request #2](https://github.com/keybase/node-bitcoin/pull/2) I submitted for node-bitcoin to allow the alternative currency private keys to be imported by a wallet.