Updated gemspec to use depenency range
Updated gemspec to use depenency range

- `rake build` was reporting dependencies were pessimistic and/or open-ended.
- License use http://spdx.org/licenses/

typekit/webfontloader,Monotype/webfontloader,ramghaju/webfontloader,typekit/webfontloader,typekit/webfontloader,ramghaju/webfontloader,ramghaju/webfontloader,Monotype/webfontloader,Monotype/webfontloader