Set version to 'git' in git repo.

mikelward · mikelward · commit 99e55513666d · 2017-09-15T13:14:59.000-07:00
When publishing to PyPI, we'll have to set it at the time of tagging,
as before.
diff --git a/ipaddr.py b/ipaddr.py
@@ -22,7 +22,7 @@
 
 """
 
-__version__ = '2.2.0'
+__version__ = 'git'
 
 import struct
 import sys
