Upgrading html5shiv to 3.7.2

Updating HTML5 Shiv to 3.7.2 which has fixes for [namespaced tag names](https://github.com/aFarkas/html5shiv/pull/135) (e.g. `<can:example>`) and [hyphenated tag names](https://github.com/aFarkas/html5shiv/pull/124) (e.g. `<can-example>`)