Fix + minor cleanup.
Avoids useless random.choices.
tree bug fixed, random tree height

Please see the comments in blocks.py concerning the textures used.
names assigned to blocks, from boksee.
Introduces decent tree generation.
Merge branch 'master' of https://github.com/boskee/Minecraft
Typo.
Fixed inventory GUI.
Merge commit '2320471b13b895db495e08315be2249bedf0ed83'

Conflicts:
	TODO.md
	blocks.py
	gui.py
	inventory.py
	main.py
Adjusts tree parameters.
Merge branch 'master' of git://github.com/avelanarius/Minecraft
Restored "hold to dig" functionality (like in MC)
Merge commit 'a552bce2c8549cd5dab18f9a9a5fe0849a450c80'
Fix default option of -terrain
Restored option to scroll in inventory.
Fix README.md
Corrected mouse clicking in inventory. You can now select items in inventory by clicking on them. After second click you can move them to quick slots.
Added new options to hide inventory GUI - by using Escape key and by clicking outside of inventory.
fix: default terrain set to 'plains' instead of 'grass'
Limit terrain argument to terrain_options.keys()