Breaks on small terminal windows

[bartekbrak]

  ...
  File "/usr/local/lib/python2.7/dist-packages/termdown.py", line 137, in wrapper
    return func(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/termdown.py", line 299, in countdown
    countdown_text if no_figlet else figlet.renderText(countdown_text),
  File "/usr/local/lib/python2.7/dist-packages/pyfiglet/__init__.py", line 748, in renderText
    return self.engine.render(text)
  File "/usr/local/lib/python2.7/dist-packages/pyfiglet/__init__.py", line 326, in render
    builder.addCharToProduct()
  File "/usr/local/lib/python2.7/dist-packages/pyfiglet/__init__.py", line 395, in addCharToProduct
    raise CharNotPrinted("Width is not enough to print this character")
pyfiglet.CharNotPrinted: Width is not enough to print this character

I sometimes display the timer on a very small window, as a tile in a tiling window manager. If I don't get the font size right termdown might break. I propose the exception is caught, acknowledged somehow but the program doesn't stop.

Should be trivial to implement.