Implement review requests

- use two empty lines before `class`
- change version numbering scheme for packages, use `url_for_version` to make things work
- specify dependency types
- add comment about temporarily moved download location
- update two packages to newer versions

var/spack/repos/builtin/packages/porta/package.py

@@ -25,6 +25,7 @@
 
 from spack import *
 
+
 class Porta(Package):
     """PORTA is a collection of routines for analyzing polytopes and
     polyhedra"""
@@ -33,7 +34,7 @@ class Porta(Package):
 
     version('1.4.1', '585179bf19d214ed364663a5d17bd5fc')
 
-    depends_on("libtool")
+    depends_on("libtool", type="build")
 
     patch("Makefile.spack.patch")