Add PythonPackage base class

- Add a PythonPackage class with build system support.
  - Support build phases in PythonPackage
  - Add a custom sanity check for PythonPackages
  - Get rid of nolink dependencies in python packages

- Update spack create to use new PythonPackage class

- Port most of Python packages to new PythonPackage class

- Conducted a massive install and activate of Python packages.
  - Fixed bugs introduced by install and activate.

- Update API docs on PythonPackage

var/spack/repos/builtin/packages/py-readme-renderer/package.py

@@ -0,0 +1,42 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class PyReadmeRenderer(PythonPackage):
+    """readme_renderer is a library for rendering "readme" descriptions
+    for Warehouse."""
+
+    homepage = "https://github.com/pypa/readme_renderer"
+    url      = "https://pypi.python.org/packages/f2/6e/ef1bc3a24eb14e14574aba9dc1bd50bc9a5e7cc880e8ff9cadd385b4fb37/readme_renderer-16.0.tar.gz"
+
+    version('16.0', '70321cea986956bcf2deef9981569f39')
+
+    depends_on('python@2.6:2.7,3.2:3.3')
+    depends_on('py-setuptools', type='build')
+    depends_on('py-bleach', type=('build', 'run'))
+    depends_on('py-docutils@0.13.1:', type=('build', 'run'))
+    depends_on('py-pygments', type=('build', 'run'))
+    depends_on('py-six', type=('build', 'run'))