Help: Random number that doesn't repeat
http://forums.coronalabs.com/topic/37674-help-random-number-that-doesnt-repeat/
Tutorial: Advanced Random Numbers
http://coronalabs.com/blog/2014/03/11/tutorial-advanced-random-numbers/
Using math.random in Corona SDK
http://hellomobiledevworld.blogspot.tw/2011/08/using-mathrandom-in-corona-sdk.html
math.random bug?
http://developer.coronalabs.com/forum/2010/01/05/mathrandom-bug
