Add new version with support of aeson-2.0 and ghc-9
Hi!
I'm actively using this library, and we're planning to migrate our project to ghc9. Since there is no open PR with similar changes, I decided to send mine.
I think there are still some questions needs to be resolved, for example updating of travis.ci configuration, and removal of Eq instance from Network.HTTP.Client.Response. But overall, I think this version should work fine.
Any suggestions are welcome, and I'll try to fix them asap.
@jonathanlking thank you for your review! I applied your suggestions and tested the build (only one build) on a couple of stack resolvers, each with different versions of aeson and text. It seems to be compiling correctly.
Regarding Travis, I totally agree with you, but I'm not sure if the migration should be done in this pull request.