new python packages

var/spack/packages/py-numexpr/package.py

+from spack import *
+import re
+
+class PyNumexpr(Package):
+    """Fast numerical expression evaluator for NumPy"""
+    homepage = "https://pypi.python.org/pypi/numexpr"
+    url      = "https://pypi.python.org/packages/source/n/numexpr/numexpr-2.4.6.tar.gz"
+
+    version('2.4.6', '17ac6fafc9ea1ce3eb970b9abccb4fbd')
+
+    extends('python')
+    depends_on('py-numpy')
+
+    def install(self, spec, prefix):
+        python('setup.py', 'install', '--prefix=%s' % prefix)

var/spack/packages/py-pytables/package.py

+from spack import *
+import re
+
+class PyPytables(Package):
+    """PyTables is a package for managing hierarchical datasets and designed to efficiently and easily cope with extremely large amounts of data."""
+    homepage = "http://www.pytables.org/"
+    url      = "https://github.com/PyTables/PyTables/archive/v.3.2.2.tar.gz"
+
+    version('3.2.2', '7cbb0972e4d6580f629996a5bed92441')
+
+    extends('python')
+    depends_on('hdf5')
+    depends_on('py-numpy')
+    depends_on('py-numexpr')
+    depends_on('py-cython')
+
+    def install(self, spec, prefix):
+        env["HDF5_DIR"] = spec['hdf5'].prefix
+        python('setup.py', 'install', '--prefix=%s' % prefix)