Update IE 10+11 IndexedDB support to "partial"

Internet Explorer 10 and 11 do not support the full range of functionality indicated in the [IndexedDB specification](http://www.w3.org/TR/IndexedDB/), and do not provide parity with other implementations (i.e. in Firefox and Chrome).  The change offered here modifies IE 10 + 11's stated support for IndexedDB to "partial".

The issues I've run into personally all revolve around IE's lack of support for array-based keys and `keyPath`s:

* not being able to use anything other than a simple string for `keyPath`
* only scalars (e.g. strings, integers, etc) may be used as keys for objects stored in IndexedDB (i.e. no arrays)
* compound indexes may not be defined

These are not bugs, but explicit points of divergence from the published specification (e.g. the `keyPath` limitation is [clearly documented on MSDN](http://msdn.microsoft.com/en-us/library/ie/hh772493%28v=vs.85%29.aspx); thus the proposal to change the advertised support level, as opposed to e.g. opening a ticket with the IE team.

These deficiencies are illustrated by this self-contained demo page:

http://codepen.io/cemerick/pen/Itymi

Any red in the reported log indicates lack of conformance.  Firefox and Chrome both work as expected.