#43 Replace pseudo random number generator

[Shun Sakuraba]

ERmod currently uses random number generator provided by the compiler (Fortran90 intrinsic). While most compiler implementations I could find use far better algorithm than the linear congruence, it is good to move on to a defined random number generator (both in terms of reproducibility and the safeness from stupid implementations). I would like to use xorshift1024* generator ( test implementation: https://bitbucket.org/shun.sakuraba/xorshiftf90 ) for that purpose.

[Shun Sakuraba]

rev. 6b516f added the RNG.