GitLab

* add un_balance to multi class

* change the calculation of label weights

commit 70f88c54f6820d4c3824d97b34042c617fb21635
Author: Guolin Ke <i@yumumu.me>
Date:   Wed Feb 22 19:40:10 2017 +0800

    futher reduce guided

commit f54620b807c68f5ac6cef521d787ca2750efe464
Author: Guolin Ke <i@yumumu.me>
Date:   Wed Feb 22 19:32:36 2017 +0800

    avoid to use guided

* Support Poisson regression

Close #233

* update docs