fix travis test build
Merge pull request #117 from evoskuil/version2

fix travis test build
Merge pull request #118 from pmienk/version2

Updated by libbitcoin-build.
Add a basic hmac_sha256 unit test
Add array_slice class
Change the hash functions to take data_slice
Make use of data_slice
Implement rfc6979 deterministic signatures
Simplify rfc6979 code using operator +
Merge pull request #120 from evoskuil/version2

Merge @swansontec rfc6979
try to make stealth_prefix ordering more logical by introducing new wrapper type.
remove unneeded bytes_to_prefix.
replace boost implementation with a custom one.
remove obsolete prefix_to_bytes()
fix stealth_match function.