TypeError in `readable_time` when watching file with target size

[normanr]

https://github.com/wardi/speedometer/blob/890df21b3a041a3ccb1594a68f913e03cf264955/speedometer.py#L943

   new_out = new_out + value + suf
              ~~~~~~~~^~~~~~~
TypeError: can only concatenate str (not "int") to str

Can be fixed by doing: new_out = new_out + str(value) + suf