Support large hashes with small curves #129
Description
Current code will abort if the order of the curve is significantly smaller than the size of provided hash. I.e. it's not possible to use SHA-512 with NIST256p.
While it's not a recommended configuration, it is well-defined, and actually used in popular protocols (e.g. TLSv1.2).
Add an option to verify() and sign() methods to change if they will accept bigger inputs and appropriately truncate them.