Use game.materials.findIndex to find correct block type. Bump v0.16.3

`game.materials.find('name')` will return the actual index of the found material within `game.materials` but not the block type index.

So I added a new method to voxel-texture to fix this called `game.materials.findIndex('name')` and updated the test to simulate how textures are loaded into the materials API more closely.

Now doing `game.setBlock([0, 0, 0], 'coal')` will work correctly. My mistake!