Adapted to Python 3

[wsourdeau]

• replaced cStringIO with io
• fixed handling of byte strings
• use integer division operator ("//") for coordinates

[wsourdeau]

Since Python 3 is becoming the norm in modern distros, I thought it would be a good idea to adapt the code to it.

[HybridDog]

Thank you for opening the Pull Request. Could you change the formulas with integer casts to use integer divisions instead? For example, change int(16 * BLOCK_SIZE/2 + BLOCK_SIZE/2) to 16 * BLOCK_SIZE // 2 + BLOCK_SIZE // 2.

[wsourdeau]

Thank you for opening the Pull Request. Could you change the formulas with integer casts to use integer divisions instead? For example, change int(16 * BLOCK_SIZE/2 + BLOCK_SIZE/2) to 16 * BLOCK_SIZE // 2 + BLOCK_SIZE // 2.

Done! I had no idea about that operator. It works very well.