updated docs to reflect min requirement of 2.1 [ci skip]

doc/install/installation.md

@@ -107,7 +107,7 @@ Then select 'Internet Site' and press enter to confirm the hostname.
 
 ## 2. Ruby
 
-_**Note:** The current supported Ruby version is 2.2.x. Ruby 2.3 is
+_**Note:** The current supported Ruby versions are 2.1.x and 2.2.x. Ruby 2.3 is
 currently not supported._
 
 The use of Ruby version managers such as [RVM], [rbenv] or [chruby] with GitLab

doc/install/requirements.md

@@ -32,7 +32,7 @@ Please consider using a virtual machine to run GitLab.
 
 ## Ruby versions
 
-GitLab requires Ruby (MRI) 2.2.x and currently does not work with version 2.3.
+GitLab requires Ruby (MRI) 2.1.x or 2.2.x and currently does not work with version 2.3.
 
 You will have to use the standard MRI implementation of Ruby.
 We love [JRuby](http://jruby.org/) and [Rubinius](http://rubini.us/) but GitLab