Add IE9 support

[poorgeek]

While Angular 1.3 supports IE9, several of the features included in the pilot require IE10. This is an effort to document what those items are so that in the event IE9 support becomes a requirement (it isn't currently), then there will be an initial list of things that will need to be addressed.

• LevelDB, which provides access to the browser's IndexedDB, throws errors and won't load the pages in IE9. Adding feature detection to either LevelDB, or wrapping our code that includes it in some, should at least get pages rendering in IE9.
• Currently using Angular's HTML5 Mode which requires the History API. Would need to switch back to the hashbang method supported by legacy browsers and then address page anchor links; e.g. the Skip Nav and the TOC on the Common Questions page.

[pkaplan]

We are seeing the LevelDB issue in IE10.

Fixing this issue would require a code change. We would either a) have to review the latest version of the library to see if it still requires an ES6 browser in which we case we have to upgrade the lib and rerun all of the tests b) add an ES6 shim that will allow us to skirt the issue in non-ES6 supported browsers.