Merge pull request #121 from evoskuil/version2

Don't rely on debug assertion to validate deserialization.
Correct bit shift error.
Merge pull request #124 from pmienk/version2

Correct bit shift error.
Add compact signatures
Add message signing and verification
stealth_blocks_size(bitsize) function.
style change: no spaces between operator and symbol for consistency
switch to data_slice for stealth stuff- enables much more flexible stealth stuff.
operator!= for stealth_prefix type.
Merge pull request #125 from libbitcoin/message

Message