Update requirements.txt

"kazoo" package is optional, required for DCS zookeeper (by default we use etcd).

"tzlocal" package is no longer required.
"cdiff" package has been replaced with "ydiff".

https://github.com/zalando/patroni/commits/master/requirements.txt

Author: vitabaks

files/requirements.txt

@@ -2,14 +2,12 @@ urllib3>=1.24.2,<1.25
 boto
 PyYAML
 six >= 1.7
-kazoo>=1.3.1
 python-etcd>=0.4.3,<0.5
 python-consul>=0.7.1
 click>=4.1
 prettytable>=0.7
-tzlocal
 python-dateutil
 psutil>=2.0.0
-cdiff
+ydiff>=1.2.0
 pexpect>=4.8.0
 ruamel.yaml>=0.16.10