Fixing ssh_config proxy_command is not included

plugins/commands/ssh_config/command.rb

@@ -37,7 +37,8 @@ module VagrantPlugins
             :ssh_user => ssh_info[:username],
             :private_key_path => ssh_info[:private_key_path],
             :forward_agent => ssh_info[:forward_agent],
-            :forward_x11   => ssh_info[:forward_x11]
+            :forward_x11   => ssh_info[:forward_x11],
+            :proxy_command => ssh_info[:proxy_command]
           }
 
           # Render the template and output directly to STDOUT

templates/commands/ssh_config/config.erb

@@ -20,3 +20,6 @@ Host <%= host_key %>
 <% if forward_x11 -%>
   ForwardX11 yes
 <% end -%>
+<% if proxy_command -%>
+  ProxyCommand <%= proxy_command %>
+<% end -%>