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/h2/default.nix

@@ -2,7 +2,6 @@
 , enum34, hpack, hyperframe }:
 
 buildPythonPackage rec {
-  name = "${pname}-${version}";
   pname = "h2";
   version = "3.0.1";