made the regression tests allow for small relative errors
Merge branch 'tests-fix'
Fixing the behaviour of bias parameter. Explanation:

The liblinear bias parameter is defined as follows (README.md at commit 7b6c6a56c1 of liblinear java):
https://github.com/bwaldvogel/liblinear-java/blob/master/README.md
"if bias >= 0, instance x becomes [x; bias]; if < 0, no bias term added (default -1)".

clj-liblinear does support the use of bias (thanks to https://github.com/lynaghk/clj-liblinear/pull/4 by @akhudek).

Currently in clj-liblinear, the only supported bias values are 0 and 1:
https://github.com/lynaghk/clj-liblinear/blob/master/src/clj_liblinear/core.clj#L54
Also, the bias=0 case results in not adding the extra featue:
https://github.com/lynaghk/clj-liblinear/blob/master/src/clj_liblinear/core.clj#L64

Therefore I make the following change:
(1) Support all bias values.
(2) Let the bias=0 case behave like documented in liblinear-java: adding an extra feature of value 0.

Reasons for the change:
    It seems reasonable for the behaviour of training to match the documented behaviour of liblinear-java.
    At least (1) is actually useful: tuning the value of the constant feature makes it possible to control the importance of regularizing the intercept vs. regularizing the other coefficients.
    Maybe (2) is useful too?
Merge branch 'bias'
renamed test
applied correction of tests to this old version (striving to extend
regression tests)
extended regression tests (to the bias=-1 case)
Merge commit '455f990' (extension of regression tests, verified to
match an old version)

Conflicts:
	test/clj_liblinear/test.clj
fixed tests to handle a small (justified) break in the regression
generalized and cleaned test code
fixed mistake in test comment
extended regression tests to newly supported cases
fixed default bias value
added core.matrix dependency
added missing :require
added FeaturesDataset protocol
renaming
simplified code a little
refactoring into protocols; compiles, but not complete yet
fixes in the refactoring to protocols, now all tests pass