UTF8 passwords work

The encode_utf8 function was altering the salt incorrectly. CryptoJS
handles UTF8 strings properly without having to convert them to the
string equivalent of byte arrays.

Note this isn't noticable with ascii salts, which all the test vectors
are.

This patch should also be made downstream to bip39.js
Merge pull request #1 from iancoleman/utf8_password

UTF8 passwords work