Actix-web: Move Askama/actix-web integration into actix-web

[djc]

I have been struggling with the Askama integrations for different web frameworks. For now, Askama is not available for actix-web 1.0 because there are conflicting dependencies between actix-web/Gotham/Rocket, all of which Askama supports. Due to coherency issues, I think the integration code will have to live inside either actix-web or Askama. I'd still be happy to do any maintenance work required on the integration, but at this point I think it would be better if the actix-web/Askama integration moves into the actix-web crate (since the latter has many more requirements on the dependency tree than Askama itself).

[fafhrd91]

I am fine with moving askama support to actix-web repo.

[fafhrd91]

Anyone want to take this task?

@actix/contributors

[fafhrd91]

whoever wants to help with this just open PR