Numeric regressions

[kkumer]

Some tests slightly failing for unknown reasons. Nothing show-stopping:

1. test_fit2 8.139 != 8.489. This is found to be due to pyminuit --> iminuit change (tests passes on initial release of py2 branch, and then fails like above after commenting out pyminuit import.) It is not clear why other fits are not affected by this package change. We should just go to iminuit and not worry about this one.

2. ntgl2 DVEMNLO_test.py:test_gepardTFFsNLO 0.54106 != 0.53283. Same for py2 and py3.