Refactor codebase

* Replace PyOpenSSL with cryptography.io
* Rename constants to const
* Drop support for uwsgi
* Use systemd to launch certidude server
* Signer automatically spawned as part of server
* Update requirements.txt
* Clean up certidude client configuration handling
* Add automatic enroll with Kerberos machine cerdentials

requirements.txt

@@ -1,21 +1,25 @@
-cffi==1.2.1
-click==5.1
-configparser
-cryptography==1.0
-falcon==0.3.0
-humanize==0.5.1
-idna==2.0
-ipaddress==1.0.16
-ipsecparse==0.1.0
 Jinja2==2.8
-Markdown==2.6.5
-pyasn1==0.1.8
-pycrypto==2.6.1
-pykerberos==1.1.8
-pyOpenSSL==0.15.1
-python-ldap==2.4.10
-python-mimeparse==0.1.4
-requests==2.2.1
-setproctitle==1.1.9
-simplepam==0.1.5
-six==1.9.0
+Markdown==2.6.6
+MarkupSafe==0.23
+argparse==1.2.1
+certifi==2016.2.28
+cffi==1.7.0
+click==6.6
+configparser==3.5.0
+cryptography==1.4
+enum34==1.1.6
+falcon==1.0.0
+humanize==0.5.1
+ipaddress==1.0.16
+Markdown==2.6.6
+ndg-httpsclient==0.4.2
+pyOpenSSL==16.0.0
+pyasn1==0.1.9
+pycparser==2.14
+python-ldap==2.4.25
+python-mimeparse==1.5.2
+requests==2.10.0
+setproctitle==1.1.10
+six==1.10.0
+urllib3==1.16
+wsgiref==0.1.2