[R] maintenance Nov 2017; SHAP plots (#2888)

* [R] fix predict contributions for data with no colnames

* [R] add a render parameter for xgb.plot.multi.trees; fixes #2628

* [R] update Rd's

* [R] remove unnecessary dep-package from R cmake install

* silence type warnings; readability

* [R] silence complaint about incomplete line at the end

* [R] initial version of xgb.plot.shap()

* [R] more work on xgb.plot.shap

* [R] enforce black font in xgb.plot.tree; fixes #2640

* [R] if feature names are available, check in predict that they are the same; fixes #2857

* [R] cran check and lint fixes

* remove tabs

* [R] add references; a test for plot.shap

R-package/demo/00Index

@@ -10,4 +10,5 @@ predict_leaf_indices            Predicting the corresponding leaves
 early_stopping                  Early Stop in training
 poisson_regression              Poisson Regression on count data
 tweedie_regression              Tweddie Regression
-gpu_accelerated                 GPU-accelerated tree building algorithms
+gpu_accelerated                 GPU-accelerated tree building algorithms
+