Other updates to readme

Author: cmaglie

README.md

@@ -20,7 +20,7 @@ http://github.com/arduino/Arduino/issues
 mailing list:
 https://groups.google.com/a/arduino.cc/forum/#!forum/developers
 
-* If you're interested in modifying or extending the Arduino software, we strongly 
+* If you're interested in modifying or extending the Arduino software, we strongly
 suggest discussing your ideas on the Developers mailing list *before* starting
 to work on them. That way you can coordinate with the Arduino Team and others,
 giving your work a higher chance of being integrated into the official release
@@ -29,10 +29,9 @@ https://groups.google.com/a/arduino.cc/forum/#!forum/developers
 Installation
 ------------
 Detailed instructions for installation in popular operating systems.  
-For Linux, see the Arduino playground: http://www.arduino.cc/playground/Learning/Linux      
-For macOS X: https://www.arduino.cc/en/Guide/MacOSX        
-For Windows :https://www.arduino.cc/en/Guide/Windows
-
+For Linux: https://www.arduino.cc/en/Guide/Linux (see also the Arduino playground page http://www.arduino.cc/playground/Learning/Linux)   
+For macOS X: https://www.arduino.cc/en/Guide/MacOSX   
+For Windows: https://www.arduino.cc/en/Guide/Windows
 
 Credits
 --------