Drop active support for Python 3.2 (and lower)
Remove LXML+no PIL from Travis build configurations

Imgages are tested with each available backend, so this
config is not necessary.
Initial support for map drawing, and opacity
Do not draw hidden layers
Improve image path handling in Image layers
Remove unused line
Improve image path handling in Image tilesets' from_dict
Update Tiled subproject
Add initial support for tilesets with individual tile images
Render image layers
Restore Python 3 compatibility
Skip all rendering tests when PIL is not available