[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/NAMESPACE

@@ -40,6 +40,7 @@ export(xgb.model.dt.tree)
 export(xgb.plot.deepness)
 export(xgb.plot.importance)
 export(xgb.plot.multi.trees)
+export(xgb.plot.shap)
 export(xgb.plot.tree)
 export(xgb.save)
 export(xgb.save.raw)
@@ -60,9 +61,12 @@ importFrom(data.table,rbindlist)
 importFrom(data.table,setkey)
 importFrom(data.table,setkeyv)
 importFrom(data.table,setnames)
+importFrom(grDevices,rgb)
 importFrom(graphics,barplot)
 importFrom(graphics,grid)
+importFrom(graphics,lines)
 importFrom(graphics,par)
+importFrom(graphics,points)
 importFrom(graphics,title)
 importFrom(magrittr,"%>%")
 importFrom(stats,median)