bump up feel++ version to 0.96.0 beta.2
allow None (see Homebrew)
fix version string
@feelpp/core disable parallel testing, see issue #88
update issue #208 make the destructor virtual
update issue #208 fix call to proper evaluation context  (RB/FEM)
introduce copy constructor needed by #208
remove white spaces
Merge branch 'develop' of https://github.com/feelpp/feelpp into develop