Adding recommended .gitattributes file.

GitHub recommends a .gitattributes file to reduce line ending noise.
Using unbiased PRNG algorithm.

Random.Next() % N does not have unbiased probability in general;
Random.Next(N) is preferred.
Correcting some typos.

DiceRoleValue to DiceRollValue, HighProbabilyDiceValuesSetup to
HighProbabilityDiceValuesSetup.