[DOC] Explain how to install a specific version (#70)

Author: tbouffard

CONTRIBUTING.md

@@ -133,9 +133,13 @@ A PR can only be merged into master by a maintainer, if all of these conditions
 
 Maintainers need to perform the following actions **in the order described here** to push out a release.
 
-#### Verify the version in [DESCRIPTION](./DESCRIPTION) file
+#### Verify the version in files
 
-Create a new PR and merge it, if the version in the [DESCRIPTION](./DESCRIPTION) file is not good.
+Check that the files are using the version to be released:
+- [DESCRIPTION](./DESCRIPTION)
+- [README](./README.md)
+
+Create a new PR and merge it, if some files require changes.
 
 #### GitHub issues and milestones update
 

README.md

@@ -36,8 +36,19 @@ install.packages('devtools')
 ```
 
 #### Install _BPMN Visualization - R Package_ from GitHub
+
+To install a dedicated version (available versions can be found in the [GitHub releases page](https://github.com/process-analytics/bpmn-visualization-R/releases)), run:
+```r
+devtools::install_github("process-analytics/bpmn-visualization-R@v0.1.1")
+```
+
+Or install the development version:
 ```r
 devtools::install_github("process-analytics/bpmn-visualization-R")
+```
+
+Then, make the library available to the current R project:
+```r
 library(bpmnVisualization)
 ```