Update fit profile and documentation

[anthonyjchriste]

This pull request

• Updates the fit profile to version 20.76
• Updates documentation link in README.md to point to the pythonhosted documentation
• Updates the Python requirements to anything > Python 2.5 since I believe this project now supports Python 3

The incorrect pip install line should update when the next release to pypi is published.

[anthonyjchriste]

I just noticed the following test is failing:

FAIL: test_int_long (test.FitFileTestCase)
Test that ints are properly shifted and scaled

Traceback (most recent call last):
File "/Users/anthony/Development/python-fitparse/tests/test.py", line 398, in test_int_long
assert f.messages[-1].fields[1].raw_value == 1739.486328125
AssertionError

Do you think this could have been caused by updating the profile?