transform Appender module into class in order to save state
  * the appender will store the file names in an array, which the controller
  passes into the View's output filenames method
refactors guard clauses in ArgumentHandler && adds View module
  * guard clauses in ruby need an explicit return to exit the method
  * commented out appender functionality to fully test arg handler
View correctly outputs filenames as they are appended to
  * Appender class now initializes with an array
flag refactor complete
  * no longer passed into the appender's methods -- the controller simply
  checks for it's existence && fires View.output_filenames