Add dev version number support

gajim/__init__.py

+import subprocess
+
 __version__ = "0.16.11"
+
+try:
+    node = subprocess.Popen('git rev-parse --short=12 HEAD', shell=True,
+        stdout=subprocess.PIPE).communicate()[0]
+    if node:
+        __version__ += '-' + node.decode('utf-8').strip()
+except Exception:
+    pass
+