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
stealth prefix now calculated from the script itself, not the data.
use a single type now stealth_prefix and remove match()
remove uint32_t from stealth_prefix- it isn't needed anymore.
Clean up prefix tests.
Use boost comparison test helpers, test one thing.
Coment cosmetic.
Fix stealth_info.ephem_pubkey (hash) misnomer.
Implement stealth_prefix input stream.
Add safe variants of from_big/little_endians.
Fix unsafe operation (guarded only by assert).
Merge pull request #126 from evoskuil/version2

Use comparative test helpers, test one thing, remove dead code.
Make unit tests more explicit, use consistent encodings.
Don't use debug assertions to validate API inputs.