Simplify segment angle calculation
Simplify segment angle calculation

Previously the angle was computed in degrees then converted to radians
via a conversion function.

This commit changes it to compute it in radians directly.

This has two advantages:
1) Less code (no need for an extra function)
2) Slightly more efficient (one less division to do in the loop)

Issue: #1

brigade/react-simple-pie-chart,dpastoor/react-simple-pie-chart,tudorilisoi/react-simple-pie-chart