--shared is now false by default in deploy setup

Most deploys are done with a dedicated user, so we will avoid messing
around with permissions and the sticky bit if not needed. People who are
deploying in a shared environment (multiple deploying users) should pass
`--shared` explicitly during setup.

Fixes #25

lib/git_deploy.rb

@@ -20,7 +20,7 @@ def init
   end
 
   desc "setup", "Create the remote git repository and install push hooks for it"
-  method_option :shared, :aliases => '-g', :type => :boolean, :default => true
+  method_option :shared, :aliases => '-g', :type => :boolean, :default => false
   method_option :sudo, :aliases => '-s', :type => :boolean, :default => false
   def setup
     sudo = options.sudo? ? "#{sudo_cmd} " : ''