Fixed 'namedtuple' bug

  In Python3 '._asdict()' was modified to return instance dict, instead
  of manually constructed 'OrderdedDict`
Added @jonathanslenders fix for #15
DECAWM now implies CR and LF

  VT220 manual is silent about CR, but `man console_codes` does require
  the cursor to appear in the _beginning_ of the next line when auto
  wrapping, see #20 for discussion
Updated 'CHANGES'
From now on 'Screen' does _not_ inherit from 'list'

  Closes #22
Added PyPy to '.travis.yml'
Updated 'CHANGES'
Bumped version
Minor 'CHANGES' update
No emails in 'AUTHORS'
Minor 'README' improvements
Switched to 'py.test' from PyPI
Merge branch 'release/0.4.8'