Fix for issue #55 - formatted Point always having zero seconds

Rounding of the arc minutes in format_degrees zeroed out the seconds field. The correct truncation of the minutes (not rounding) is done by the format string.

Before:
>>> from geopy import Point
>>> p = Point('51 19m 12.9s N, 0 1m 24.95s E')
>>> p.format()
'51 19m 0.0s N, 0 1m 0.0s E'

After:

>>> from geopy import Point
>>> p = Point('51 19m 12.9s N, 0 1m 24.95s E')
>>> p.format()
'51 19m 12.9s N, 0 1m 24.95s E'