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'
```
The ```round()``` here removed the fractional part of the arcminutes and rounded it up/down to the nearest minute. This meant the ```arcminutes - int(arcminutes)``` in the next line always returned zero.