Fix version info

Author: heitzmann

README.md

@@ -59,7 +59,7 @@ Help support gdspy development by [donating via PayPal](https://www.paypal.com/c
 
 ## History of changes
 
-### Upcoming
+### Version 1.3.1 (Jun 29, 2018)
 * `PolygonSet` becomes the base class for all polygons, in particular `Polygon` and `Rectangle`.
 * Added `Cell.remove_polygons` and `Cell.remove_labels` functions to allow filtering a cell contents based, for example, on each element's layer.
 * Added `PolygonSet.scale` utility method.

gdspy/__init__.py

@@ -55,7 +55,7 @@
         category=ImportWarning,
         stacklevel=2)
 
-__version__ = '1.2.1'
+__version__ = '1.3.1'
 
 _halfpi = 0.5 * numpy.pi
 _directions_dict = {'+x': 0, '+y': 0.5, '-x': 1, '-y': -0.5}