v0.13.0

What's new

• Default headers now include User-Agent
• Update RedirectPolicy to allow creating Custom policies, which utilize uri
• Support for Authentication (Basic and Bearer)
• New dependencies
  • base64 ^0.22.1
  • zeroize ^1.8.1

Breaking changes

• Content-Length header is automatically added, when body is set for the request as per #41 by @cjqpker, also mentioned in #39