Playscii 0.9.9

Art Mode:

• Horizontal/vertical flip operation for Art documents
• added Macintosh II color palette

Game Mode improvements:

• Fireplace example game, with documentation
• added GameWorld.pause_music and GameWorld.resume_music
• added GameWorld.allow_pause for disabling player pause control entirely
• added GameObject.mouse_wheeled for handling mouse wheel movement on hovered objects
• added CharacterSet.get_solid_pixels_in_char for getting visual density of a given character
• small fixes to "autoplay" mode ie game distribution
• fixed a None vs 0 confusion logic bug in Art.write_string

platform work:

• some groundwork for running Playscii on the Raspberry Pi 2/3 - doesn't work at all yet; if you've gotten a PyOpenGL program running on the Pi please let me know how you did it!
• support GPUs without Vertex Array Objects (as part of above), possibly loosening system requirements
• more tolerant GLSL version detection
• better shader compile error logging
• handle possible GLU.gluProject exception in vector.world_to_screen