Alpha 0.5.0

Update 0.5.0. added glowstone, paintings, melons, and the Nether Reactor. Of the additions and changes there were:
 * Melons and their respective seeds
 * Paintings
 * Glowstone
 * The Nether Reactor (spawns a spire of obsidian)
 * Glowing obsidian
 * Nether Rector Core
 * Zombie Pigmen (were naturally hostile, missing the hat layer, and burned in daylight)
 * Food heals more health
 * Sleeping heals health
 * Mushrooms can now be farmed
 * Farmland turns into dirt when trampled
 * Health is now displayed at the top left of the screen instead of above the hotbar