Allow numeric ports for proxy sites (#984)

Fixes #910 by casting the port to a string and therefore allowing string
concatenation in [z-ray
cleanup](https://github.com/laravel/homestead/blob/master/scripts/homestead.rb#L269)

It's probable that this will occur in other places, i will look around,
but in the meantime, this fixes the most common scenario that is a fresh
installation with its defaults.

scripts/homestead.rb

@@ -266,7 +266,7 @@ def self.configure(config, settings)
             end
           else
             config.vm.provision 'shell' do |s|
-              s.inline = 'rm -rf ' + site['to'] + '/ZendServer'
+              s.inline = 'rm -rf ' + site['to'].to_s + '/ZendServer'
             end
           end
         end