* Implement Transform class. * Add tests for softmax. * Use Transform in regression, softmax and hinge objectives, except for Cox. * Mark old gpu objective functions deprecated. * static_assert for softmax. * Split up multi-gpu tests.
* Add travis sanitizers tests. * Add gcc-7 in Travis. * Add SANITIZER_PATH for CMake. * Enable sanitizer tests in Travis. * Fix memory leaks in tests. * Fix all memory leaks reported by Address Sanitizer. * tests/cpp/helpers.h/CreateDMatrix now returns raw pointer.