Add support for Quartz ore and redstone block

See #863
First pass an rendering comparators

See #863
Load textures from the new textures folder (intead of terrain.png)

See #863
Handle HD textures and animated textures
Weighted pressure plates

See #863
Support for the Daylight sensor

See #863
Added:
-droppers (still TODO vertical orientations)
-activator rails
-quartz stairs
-trapped chests
-quart blocks (all types)

Also moved restone block and quartz ore block code to the end of the file.
Redstone now connects to trapped chests.
Updated png-it.py, now it has --autocrop option.
1.5 Pre-Release updates/fixes
Fix for Ender Portal Frame, w/eye of ender, in all orientations
Minor fix for Comparator back torches
Update to lighting on Quartz stairs
Added Quartz Half Slabs
Added Hoppers
Screenshot: http://i.imgur.com/nB2Nzp6.jpg
Merge pull request #895 from skeight/snapshot

1.5 Pre-Release updates/fixes
- Fixed lighting for anvils.
- Added vertical orientations for dispensers and droppers
- Added special cases of stone and sandstone double slabs
Fix error in documentation

No parenthesis on the import statement.
Fixed Python3 error message

Up to this point, when launching overviewer with python3, overviewer would
(ironic as it is) crash on the line where the error message would be displayed
with a syntax error. I have now fixed this.
travis update, /dev/shm no longer avail, so 1 proc only
Merge branch 'snapshot'
Merge PR #903
Merge PR #902
Fixed paths with square brackets in them.