bumps bindata dependency

adds optional dynamic key selection

# You may dynamically decide the key by passing a block to the decode function
# the algorithm is optional, you can omit it to use algorithm defined in the header
payload, header = JWT.decode(token, JWT::Algorithm::HS256) do |header, payload|
  "the key"
end

adds crystal version supported in shard.yml

adds crystal 0.36.0 support

use .final instead of .digest related to changes in crystal-lang/crystal#8426
thanks @bcardiff

• improve base64 encoding performance #30
• prevent timing attacks on HMAC signatures #31

thanks @jamescook

payload decoding now returns a JSON::Any structure for the body instead of a Hash(String,JSON::Any)
this allows for more flexible playload contents if validation is not required.

fixes compiler warnings
improves error/exception feedback

adds support for ECDSA (ES256, ES384, ES512) tokens

adds support for the latest version of openssl_ext