Version 5.7.0 release

Version v5.6.0

Version v5.5.2

Merge pull request twitchtv#137 from jtvjorge/urllib3_cve_2018_20060

update urllib3 version for CVE-2018-20060

Increment to version 5.5.0

Version 5.4.2

Version 5.4.1

Version v5.4.0

Regenerate with v5.3.0

Release version v5.2.0

This release includes the following changes:

- Handling of Content-Type headers with name=value pairs after the
  MIME type is now correct.

- Context values describing the requested service, package, and method
  are now available to HTTPClients passed to generated Twirp clients.

- Generated clients no longer emit logs to the standard library logger
  under any circumstances. Instead, they will return any error
  encountered closing an HTTP response body if they found no other
  errors during the request. If they hit other errors, then HTTP
  response body close errors are ignored.

- The vendor directory is now committed. This should make installation
  of protoc-gen-twirp more straightforward.