2.1.1 - Bug Fixes for ECDSA Signatures & CSR encoding

This release is a bug fix release.

Changes

• ECDSA signatures are now properly supported in AlgorithmIdentifier and can be used when signing CSRs and Certificates.
• CSR encoding no longer encodes an empty attributes array and instead skips encoding the attributes fields altogether.
• AuthorityKeyIdentifier now asserts that the serial number is non-negative.