Mapping of phi to all 4 quadrants

[szepfalvibalint]

I have tested it with a small number of Pythia8 data.

[szepfalvibalint]

On the Travis CI test, the testing of the failure was:
pt, eta, phi = convert_px_py_pz(-1, 0, 0)
Here the test was requiring pt=1 and phi=0, whereas phi should be pi or -pi.