aligner's arugments passing by string, StringIO, and file object

I modify Aligner.__init__ like:

      if options['srcfile']:
        try:
          self.src = open(options['srcfile'], 'rU')
        except:
          if isinstance(options['srcfile'], io.TextIOBase):
            self.src = options['srcfile']
          else:
            self.src = io.StringIO('\n'.join(options['srcfile']))

I also make tests with texts generated by python 3.
fix #3