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/cddlib/package.py

@@ -25,21 +25,32 @@
 
 from spack import *
 
+
 class Cddlib(Package):
-    """The C-library  cddlib is a C implementation of the Double Description 
+    """The C-library cddlib is a C implementation of the Double Description 
     Method of Motzkin et al. for generating all vertices (i.e. extreme points)
     and extreme rays of a general convex polyhedron in R^d given by a system 
     of linear inequalities"""
     homepage = "https://www.inf.ethz.ch/personal/fukudak/cdd_home/"
+    # This is the original download url. It is currently down [2016-08-23],
+    # but should be reinstated or updated once the issue is resolved.
     # url      = "ftp://ftp.ifor.math.ethz.ch/pub/fukuda/cdd/cddlib-094h.tar.gz"
     url      = "http://pkgs.fedoraproject.org/lookaside/pkgs/cddlib/cddlib-094h.tar.gz/1467d270860bbcb26d3ebae424690e7c/cddlib-094h.tar.gz"
 
-    version('094h', '1467d270860bbcb26d3ebae424690e7c')
+    def url_for_version(self, version):
+        # Since the commit id is part of the version, we can't
+        # auto-generate the string, and we need to explicitly list all
+        # known versions here. Currently, there is only one version.
+        if str(version) == '0.94h':
+            return "http://pkgs.fedoraproject.org/lookaside/pkgs/cddlib/cddlib-094h.tar.gz/1467d270860bbcb26d3ebae424690e7c/cddlib-094h.tar.gz"
+        raise InstallError("Unsupported version %s" % str(version))
+
+    version('0.94h', '1467d270860bbcb26d3ebae424690e7c')
 
     # Note: It should be possible to build cddlib also without gmp
 
     depends_on("gmp")
-    depends_on("libtool")
+    depends_on("libtool", type="build")
 
     def install(self, spec, prefix):
         configure("--prefix=%s" % prefix)