def quadkey level, x, y
			x_chars = x.bin_str(level).split ""
			y_chars = y.bin_str(level).split ""

			y_chars.zip(x_chars).flatten.join("").to_i(2).to_s(4).rjust(level, "0")
		end
def quadkey level, x, y
			x_chars = x.bin_str(level).split ""
			y_chars = y.bin_str(level).split ""

			y_chars.zip(x_chars).flatten.join("").to_i(2).to_s(4).rjust(level, "0")
		end
Calculates quadkey for tile (<x>, <y>) on level <level_number>
 The process is kind of complex, here's what it does:
 1. Converts x, y to binary string
 2. Interleave the bits of y and x coordinates
 3. Interprate the result as a base-4 number (with leading zeros maintained)