Adds sudo for gem command

mamaar · mamaar · commit 21b0139c1ab4 · 2018-10-16T07:27:05.000+02:00
diff --git a/README.md b/README.md
@@ -78,7 +78,7 @@ $ cp chromedriver /usr/local/bin
 Install the required Ruby gem.
 
 ```
-$ gem install watir
+$ sudo gem install watir
 ```
 
 Generate the tests.
