Update gemspec
Update gemspec

nicolas-brousse/rrdtool_lib-gem,nicolas-brousse/rrdtool_lib-gem,nicolas-brousse/rrdtool_lib-gem,nicolas-brousse/rrdtool_lib-gem,nicolas-brousse/rrdtool_lib-gem,nicolas-brousse/rrdtool_lib-gem,nicolas-brousse/rrdtool_lib-gem,nicolas-brousse/rrdtool_lib-gem,nicolas-brousse/rrdtool_lib-gem