Support / test newer versions of dependencies

[uSpike]

Because the following version constraints are defined:

apispec = {version = "^1.0",optional = true}
pyyaml = {version = "^3.13",optional = true}

Only apispec 1.x and pyyaml 3.13.x will be used/tested when flama[schema] is installed.

apispec is on version 3 and pyyaml is at 5 now. There are numerous useful changes in those projects that can be integrated into flama.

[perdy]

The new version of Flama (v0.12) now supports apispec 3 and pyyaml 5.

Thanks!