Add implementation for doubled char width (for better aspect ratio)

- Add implementation for doubled char width (for better aspect ratio
  on most terminals), but not yet enabled by default.
- Fix too-short top and bottom margins (2 blocks instead of 4),
  so fix t/01-slashdot.t
Change constructor to allow options

Change the internal representation of the object to allow additional
options to be given to the constructor and stored.
Make options 'wide' and 'filler' available.