Gemfile: remove unused dependencies

The point of calling ```gemspec``` is to tell bundle that the dependencies are listed in there so I think really none of these dependencies should be here but got rid of the commented out ones and left ```gem 'packable', ">= 1.3.5"  # for Matlab IO``` since they are clearly not doing anything and I did not want to have to search out the versioning to add packable to gemspec. :-)