update installation code for rtools (#65)

learners/setup.md

@@ -121,18 +121,31 @@ These installation steps could ask you `? Do you want to continue (Y/n)` write `
 
 ### do you get an error with EpiNow2?
 
-Windows users will need a working installation of `Rtools` in order to build the package from source. `Rtools` is not an R package, but a software you need to download and install. We suggest you to follow [these steps](http://jtleek.com/modules/01_DataScientistToolbox/02_10_rtools/#1):
+Windows users will need a working installation of `Rtools` in order to build the package from source. `Rtools` is not an R package, but a software you need to download and install. We suggest you to follow:
 
-1. Download the `Rtools` installer from <https://cran.r-project.org/bin/windows/Rtools/>
-2. Install `Rtools` with default selections
+<!-- reference [these steps](http://jtleek.com/modules/01_DataScientistToolbox/02_10_rtools/#1) -->
 
-To verify your installation follow these two steps:
+1. **Verify `Rtools` installation**. You can do so by using Windows search across your system. Optionally, you can use `{devtools}` running: 
 
-3. Install `{devtools}` -->  `install.packages("devtools")`
-4. Verify Rtools installation with --> `devtools::find_rtools()`
+```r
+if(!require("devtools")) install.packages("devtools")
+devtools::find_rtools()
+```
+
+If the result is `FALSE`, then you should do step 2.
+
+2. **Install `Rtools`**. Download the `Rtools` installer from <https://cran.r-project.org/bin/windows/Rtools/>. Install with default selections.
+
+3. **Verify `Rtools` installation**. Again, we can use `{devtools}`:
+
+```r
+if(!require("devtools")) install.packages("devtools")
+devtools::find_rtools()
+```
 
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+
 ::::::::::::::::::::::::::::: spoiler
 
 ### do you get an error with epiverse-trace packages?