Changelog for http-rfc7807-0.2.0.0

For latest version of this document see ChangeLog.md on GitHub.

(breaking change) Function rfc7807ServerError sets the value of title field is set to HTTP reason from Servant's ServerError by default. User can still override it as before, but this is a breaking change as it changes the expected output.
(breaking change) Type variable body is now first in the definition of rfc7807ServerError. If you've used TypeApplications when calling rfc7807ServerError function then this may be a breaking change for you.
(change) Support servant-server-0.15 in addition to currently supported versions. We are planning to drop the support once again in next major release. See @servant-server-1.16 ChangeLog to see what it entails.
Documentation updates

Initial release