cleaned up client crypto dependencies

added a new scrypt library that is about 3x faster as
emscrypt.js. It should be factored into its own module
on npm eventually.

also updated the npm sjcl dependency to 1.0.0 (official)
and removed the sjcl-codec-bytes dep by using hex instead.
Merge pull request #271 from dannycoates/emscrypt

cleaned up client crypto dependencies
Added a short dicussion about the motivation for the raw_password API
Merge pull request #272 from ckarlof/raw_password_docs

Added a short dicussion about the motivation for the raw_password API
fixed broken test after #269