Return nil for tile position if index is out of bounds
Tileset#tile_position now also returns the position on the tileset in tiles
Properly convert 1-based tileset index to 0-based pixel index
Revert previous commit and instead return nil for earlier indices
Damned off-by-one errors!
Update comments
Add TileLayer#index2pos and TileLayer#pos2index
Can't calculate indices without a map with a width
No, I WON'T repeat that note about the two hardest problems in computer science here again
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Yield correct number of values for empty fields in TileLayer#each_tile
Expose methods for tileset tile dimensions calculation
add next_first_gid into Map class
Merge remote-tracking branch 'upstream/master'

Conflicts:
	lib/tiled_tmx/tileset.rb