Updated argsToPath to support more than two args

- According to the documentation Titanium.Filesystem.getFile "takes
  a variable number of arguments, where each argument is treated as
  a path component."
  (see http://docs.appcelerator.com/titanium/latest/#!/api/Titanium.Filesystem-method-getFile)

  The argsToPath method in uglify was concatenating arguments together
  but was not separating them with path separators when more than two
  arguments were used in Titanium.Filesystem.getFile.

  For example if the original source looked like:
  Ti.Filesystem.getFile(Ti.Filesystem.resourcesDirectory, "a_folder", "a_file");

  The argsToPath method would generate:
  Ti.Filesystem.getFile(__p.file(Ti.Filesystem.applicationDataDirectory + require("/api/TiShadow").currentApp + "/" + ("a_folder" + "a_file")))

  The file would not be found because there was no path separator
  between the folder and the file.

- I added two test cases in the filesystem.js expected/fixtures
  files to demonstrate the behavior (you can see this if you don't
  apply the change to uglify).
Merge pull request #278 from sztn/argsToPath_fix

Updated argsToPath to support more than two arguments per Ti.Filesystem.getFile documentation