[CHORE] Modified functions not to overwrite entire prototype
[FIX] Replaced Account.is_valid() with Account.isValid()
[FEATURE] New Message class for sigs on arbitrary data

This includes supporting files that can sign arbitrary data
with a signature that enables public key recovery. It also
includes the PublicKeyValidator class that can verify whether
a given public key is active for an account by looking in its
AccountRoot.
[CHORE] Added account param to signing functions
[FIX] Point coordinates should be converted to psuedo mersenne primes
[CHORE] Added pre-built sjcl with additional functions included
[FIX] Handling public key validation for unfunded accounts
[CHORE] Changed variable name to make Stefan happier
[CHORE] Merged PubKeyValidator into Account class
Merge pull request #72 from emschwartz/message-signing

[FEATURE] New Message class for sigs on arbitrary data