add pyasn1 as a dependency
add decode_rfc6979_signature helper for DSA/ECDSA
add encode_rfc6979_signature and refactor tests to use it
add changelog entry
error if signature has trailing bytes
assign tuple to multiple vars for better readability
catch PyAsn1Error when decoding rfc6979 signature
add comment describing how the ASN.1 sequence in a test is invalid
catch PyAsn1Error for encoding signature as well
directly test r, s for integer-ness
Stupid mistake number one billion.
Merge pull request #1502 from reaperhulk/fix-1285

Support decoding RFC 6979 signatures to (r, s)