Release 3.0.0

About SwiftRandom release 3.0.0:

1. The program is reorganized so that it uses struct's instead of class'es.
   Among other things, this improves the performance considerably, especially for the
   Mersenne Twister generators.

2. The MT32 Mersenne Twister has a jump function which advances the generator state
   as if 2^128 calls to the nextUInt32() method had been performed a number of times.

3. Release 3.0.0 is backwards compatible with release 2.1.0 in the sense that release
   3.0.0 bitgenerators and release 2.1.0 bitgenerators will produce identical sequences
   of values if they are initialized with the same seed.