Mention how to install 'rubygems' (home-assistant#2890)

vrs01 · fabaff · commit 14d2c3ce9392 · 2017-06-26T18:32:12.000+02:00
* Update installation.markdown

* Update command
diff --git a/source/_docs/ecosystem/hadashboard/installation.markdown b/source/_docs/ecosystem/hadashboard/installation.markdown
@@ -84,9 +84,17 @@ $ cd hadashboard
 
 ### {% linkable_title 2. Install Dashing and prereqs %}
 
-Essentially, you want to make sure that you have Ruby installed on your local machine. Then, install the Dashing gem:
+Essentially, you want to make sure that you have Ruby installed on your local machine. 
 
-``` bash
+For Debian based distribution do:
+
+```bash
+$ sudo apt-get install rubygems
+```
+
+Then, install the Dashing gem:
+
+```bash
 $ gem install dashing
 ```
 
