peak_curvature library method fixed up to:
* work with None slices
* work on all valid slices (not just the first)
* accept backward steps when not using truck_and_trailer method
* raise ValueError if unknown curve_sense provided
* only return index if curvature is the correct type
Raise error if step is bigger than 1 or -1 as index returned is not accurate
Merge branch 'master' of github.com:FlightDataServices/FlightDataAnalyzer