Add ability to place blocks
Store block counter in App
Revert "Store block counter in App"

This reverts commit 8077d45f7d7eb7cde35abd337232409b98c3d79a.
Add App.place_block
Return references to blocks instead of blocks
Fix spawning inside the floor, and don't store block ids with Block
objects
Add all geometry for blocks in App.place_block
Fix last commit
Add block_id_to_index lookup
Add Block.id, complete block_id_to_index lookup when manipulating blocks
Improve readability of code
Check for intersections when placing blocks
Merge remote-tracking branch 'origin/master' into place-blocks

* origin/master: (34 commits)
  add a HUD with a cursor
  cleanups, higher framerate
  hide cursor
  move dirt blocks
  use fontloader
  assert_eq
  make text work and add texture shading things
  cleanups/minor tweaks
  clean up GLBuffers
  random spacing
  fonts!
  wat
  yay iterators
  fix build
  broaden FOV
  use raw strings
  less indirection
  increase friction
  jump cap
  add TODO
  ...

Conflicts:
	src/main.rs
Merge remote-tracking branch 'origin/master' into place-blocks

* origin/master:
  Update for https://github.com/bfops/piston/commit/091c657b5fa9f63eb99674cbd674c1fd285a5507
Fix error from merge with master
Make it run after merge with master
Delete blocks using block_id
Merge branch 'master' into place-blocks

* master:
  update shaders?

Conflicts:
	src/main.rs
Remove unused Color code
Remove duplicated instance of selection_color function