[ENHANCEMENT] Grid size should be limited.

[me_a_doge]

Sounds awful but is there anyone want to play a 100x100 grid?

We should limit the grid's size down to 8x8, 16x16 and 16x30. Here's the link.

And when I say limit the size, I means we should make bombs constant, not a random variable.

[Hoang-Quan, Tran]

Noted.