Rendera 0.2.9

Includes self-contained binaries for 32 and 64-bit Windows. Changes include:

-The undo/redo system has been optimized for memory usage.
-Added gamma-corrected blending mode (Non-Linear).
-Fixed a possible crash after rotating an image 90 degrees.
-Optimized viewport rendering when zoomed in so it should work better on slower computers.
-Minor GUI changes.