Merge pull request #24 from amscins/master

The test_direction_readback fails, because gpio_get_direction wasn't properly null terminating the direction string
Fix PWM duty cycle so 0 is off and 100 is on.  Set polarity to 0 by default.
bump version to 0.0.14 and update changelog
bump version to 0.0.15
remove unused variables
Update README.rst
Update CHANGELOG.rst
fix for polarity not getting set properly, add polarity as optional parameter in start
Update CHANGELOG.rst
Add polarity example for PWM.