Re-remove the psutil dependency from setup.py

setup.py

@@ -40,7 +40,6 @@ install_requires = [
     'configobj',
     'cryptography>=0.7',  # load_pem_x509_certificate
     'parsedatetime>=1.3',  # Calendar.parseDT
-    'psutil>=2.2.1',  # 2.1.0 for net_connections and 2.2.1 resolves #1080
     'PyOpenSSL',
     'pyrfc3339',
     'python2-pythondialog>=3.2.2rc1',  # Debian squeeze support, cf. #280
@@ -70,6 +69,7 @@ dev_extras = [
     'coverage',
     'nose',
     'pep8',
+    'psutil>=2.2.1',  # for tests, optional
     'pylint==1.4.2',  # upstream #248
     'tox',
     'twine',