Fix setuptools handling in Python packages.

- add setuptools dependencies to packages that need it.
- remove setuptools from packages that do not need it.

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

@@ -34,5 +34,6 @@ class PyPeriodictable(PythonPackage):
 
     version('1.4.1', '7246b63cc0b6b1be6e86b6616f9e866e')
 
+    depends_on('py-setuptools', type='build')
     depends_on('py-numpy', type=('build', 'run'))
     depends_on('py-pyparsing', type=('build', 'run'))