Catch silent non-perturbative running problem by checking if the
maximum error is finite.  I hereby assume that if there is a nan in an
array, maxCoeff() will return nan.  This means that errmax is always
nan if there is a nan in the beta function.  Doing the check this way
is much cheaper than checking each beta function for nan.
Put all generated classes into a `flexiblesusy' namespace.
I've chosen this name because it matches the package name.