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/stringtemplate/default.nix

@@ -2,11 +2,10 @@
 
 buildPythonPackage rec {
   pname = "PyStringTemplate";
-  name = "${pname}-${version}";
   version = "3.2b1";
 
   src = fetchurl {
-    url = "http://www.stringtemplate.org/download/${name}.tar.gz";
+    url = "http://www.stringtemplate.org/download/${pname}-${version}.tar.gz";
     sha256 = "0lbib0l8c1q7i1j610rwcdagymr1idahrql4dkgnm5rzyg2vk3ml";
   };