Add tip on string manipulation when writing a Cask

CONTRIBUTING.md

@@ -249,11 +249,26 @@ Example:
 	app 'TexmakerMacosxLion/texmaker.app'
 	```
 
-### Indenting
+### Style guide
 
 All Casks and code in the homebrew-cask project should be indented using two
 spaces (never tabs).
 
+If relevant, you may also use string manipulations to improve the maintainability of your Cask. Here's an example from `Lynkeos.app`:
+
+```ruby
+cask :v1 => 'lynkeos' do
+  version '2.10'
+  sha256 'bd27055c51575555a1c8fe546cf057c57c0e45ea5d252510847277734dc550a4'
+
+  url "http://downloads.sourceforge.net/project/lynkeos/lynkeos/#{version}/Lynkeos-App-#{version.gsub('.', '-')}.zip"
+  name 'Lynkeos'
+  homepage 'http://lynkeos.sourceforge.net/'
+  license :gpl
+
+  app "Lynkeos-App-#{version.gsub('.', '-')}/Lynkeos.app"
+end
+```
 
 ## Testing Your New Cask