pythonPackages: remove name attribute`

The `buildPython*` function computes name from `pname` and `version`.
This change removes `name` attribute from all expressions in
`pkgs/development/python-modules`.

While at it, some other minor changes were made as well, such as
replacing `fetchurl` calls with `fetchPypi`.

pkgs/development/python-modules/acme/default.nix

@@ -18,7 +18,6 @@ buildPythonPackage rec {
   inherit (certbot) src version;
 
   pname = "acme";
-  name = "${pname}-${version}";
 
   propagatedBuildInputs = [
     cryptography pyasn1 pyopenssl pyRFC3339 pytz requests six werkzeug mock