Bump version to v0.18.0

Author: wojcikstefan

mongoengine/__init__.py

@@ -23,12 +23,13 @@
            list(signals.__all__) + list(errors.__all__))
 
 
-VERSION = (0, 17, 0)
+VERSION = (0, 18, 0)
 
 
 def get_version():
-    """Return the VERSION as a string, e.g. for VERSION == (0, 10, 7),
-    return '0.10.7'.
+    """Return the VERSION as a string.
+
+    For example, if `VERSION == (0, 10, 7)`, return '0.10.7'.
     """
     return '.'.join(map(str, VERSION))