Revert "Fixes #686"

This reverts commit 19984c7.
Necessary because data.tree not existant on R <3.5

Author: lorenzwalthert

vignettes/customizing_styler.Rmd

@@ -242,10 +242,31 @@ line breaks and spaces. Let's first create the nested parse table.
 code <- c("add_one <- function(x) { x + 1 }")
 ```
 
-```{r}
+``` r
 styler:::create_tree(code)
 ```
 
+     ##                                              levelName
+     ## 1  ROOT (token: short_text [lag_newlines/spaces] {id})
+     ## 2   °--expr:  [0/0] {23}                              
+     ## 3       ¦--expr:  [0/1] {3}                           
+     ## 4       ¦   °--SYMBOL: add_o [0/0] {1}                
+     ## 5       ¦--LEFT_ASSIGN: <- [0/1] {2}                  
+     ## 6       °--expr:  [0/0] {22}                          
+     ## 7           ¦--FUNCTION: funct [0/0] {4}              
+     ## 8           ¦--'(': ( [0/0] {5}                       
+     ## 9           ¦--SYMBOL_FORMALS: x [0/0] {6}            
+     ## 10          ¦--')': ) [0/1] {7}                       
+     ## 11          °--expr:  [0/0] {19}                      
+     ## 12              ¦--'{': { [0/1] {9}                   
+     ## 13              ¦--expr:  [0/1] {16}                  
+     ## 14              ¦   ¦--expr:  [0/1] {12}              
+     ## 15              ¦   ¦   °--SYMBOL: x [0/0] {10}       
+     ## 16              ¦   ¦--'+': + [0/1] {11}              
+     ## 17              ¦   °--expr:  [0/0] {14}              
+     ## 18              ¦       °--NUM_CONST: 1 [0/0] {13}    
+     ## 19              °--'}': } [0/0] {15}
+
 ```{r}
 pd <- styler:::compute_parse_data_nested(code)
 ```