* Add bindings for serialization.
* Change `xgb.save.raw' into full serialization instead of simple model.
* Add `xgb.load.raw' for unserialization.
* Run devtools.
* [R] xgb.save must work when handle in nil but raw exists
* [R] print.xgb.Booster should still print other info when handle is nil
* [R] rename internal function xgb.Booster to xgb.Booster.handle to make its intent clear
* [R] rename xgb.Booster.check to xgb.Booster.complete and make it visible; more docs
* [R] storing evaluation_log should depend only on watchlist, not on verbose
* [R] reduce the excessive chattiness of unit tests
* [R] only disable some tests in windows when it's not 64-bit
* [R] clean-up xgb.DMatrix
* [R] test xgb.DMatrix loading from libsvm text file
* [R] store feature_names in xgb.Booster, use them from utility functions
* [R] remove non-functional co-occurence computation from xgb.importance
* [R] verbose=0 is enough without a callback
* [R] added forgotten xgb.Booster.complete.Rd; cran check fixes
* [R] update installation instructions
* [R-package] JSON tree dump interface
* [R-package] precision bugfix in xgb.attributes
* [R-package] bugfix for cb.early.stop called from xgb.cv
* [R-package] a bit more clarity on labels checking in xgb.cv
* [R-package] test JSON dump for gblinear as well
* whitespace lint
* [R] do not remove zero coefficients from gblinear dump
* [R] switch from stringr to stringi
* fix#1399
* [R] separate ggplot backend, add base r graphics, cleanup, more plots, tests
* add missing include in amalgamation - fixes building R package in linux
* add forgotten file
* [R] fix DESCRIPTION
* [R] fix travis check issue and some cleanup
