Add py-csvkit package

This adds the py-csvkit package and needed dependencies for working with
csv files.

var/spack/repos/builtin/packages/py-xlrd/package.py

@@ -0,0 +1,16 @@
+from spack import *
+
+class PyXlrd(Package):
+    """
+    Library for developers to extract data from Microsoft Excel (tm)
+    spreadsheet files
+    """
+    homepage = 'http://www.python-excel.org/'
+    url      = "https://pypi.python.org/packages/source/x/xlrd/xlrd-0.9.4.tar.gz"
+
+    version('0.9.4', '911839f534d29fe04525ef8cd88fe865')
+
+    extends('python')
+
+    def install(self, spec, prefix):
+        python('setup.py', 'install', '--prefix=%s' % prefix)