(-1)^i for integer i replaced with ?: test
Invoking std::pow to compute this was both unnecessary and caused
confusion for some older compiler versions. Replaced by a ternary
operator test ? : as there are only two possible outcomes.
Merge branch 'release-3.0.1-branch' of github.com:jeanluct/braidlab into release-3.0.1-branch
Merge branch 'release-3.0.1-branch' into develop