dynamically detect terminal width to line wrap appropriately #90

instead of always wrapping at IceCreamDebugger.lineWrapWidth characters, dynamically detect the terminal width with os.get_terminal_size()

os.get_terminal_size() isnt implemented in py2, so os.environ['COLUMNS'] can be read directly as a fallback

if the terminal width cant be detected, then fall back to IceCreamDebugger.lineWrapWidth

see #89