Merge branch 'unity'

Conflicts:
	.gitignore
	R-package/src/xgboost_R.cpp
	src/gbm/gblinear-inl.hpp
	tools/xgcombine_buffer.cpp

.gitignore

@@ -2,7 +2,7 @@
 *.slo
 *.lo
 *.o
-
+*.page
 # Compiled Dynamic libraries
 *.so
 *.dylib
@@ -45,3 +45,11 @@ Debug
 *save
 *csv
 .Rproj.user
+*.cpage.col
+*.cpage
+xgboost
+xgboost.mpi
+xgboost.mock
+train*
+rabit
+