add virtual server routes
register and apply MIME type for versioning
 model validations

 * uses Filesize gem, so save sizes as strings
 * share validations between host_server and virtual_server models
 * edit host_server migration (OK because i'm the only developer)
 * check against null and limit string length directly in ActiveRecord

 Please enter the commit message for your changes. Lines starting
add virtual_server fabricator
edit rails_helper for headers var
remove unable-to-find conditional; AR covers this
add virtual server model spec
edit request_helpers.rb

* symbolize json in helper
* add headers helper; see rails_helper
edit host_servers_spec

* symbolize json
* use Fabrication for params
* use headers helper instance variable
* test status codes symbol name instead of num and message explicitly
add virtual_servers_spec
add virtual_servers_controller