I assume there is a typo here because expected `avg_hr` should be 80, right?. Actually I get an error when running tests (`nosetests` from project root):
```
======================================================================
FAIL: test_hrFromLaps_handlingOfNone (pytrainer.test.record_test.RecordTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/david/pytrainer/working/pytrainer/test/record_test.py", line 58, in test_hrFromLaps_handlingOfNone
    self.assertEqual(self.record.hrFromLaps(laps), (160, 180))
AssertionError: Tuples differ: (80, 180) != (160, 180)

First differing element 0:
80
160

- (80, 180)
?  ^

+ (160, 180)
?  ^^
```