a regression test

Thank you for your quick replies to the recent issues!

Preparing for the changes, this pull request suggests some basic regression test.

To support the test, some auxiliary functions are added:
- a function for getting model's coefficients (clj-liblinear.core)
- a function for resetting liblinear's pseudorandom number generator (clj-liblinear.core)
- functions for generating pseudorandom data (clj-liblinear.test)

What do you think?