Drive initial search from URL query string

Fixes #82
> is this if necessary?

It's a stylistic thing AFAIK.  If the maintainers dislike it, I'm fine with changing it.

> `document.activeElement` is always truthy

Usually but _not_ always, e.g. `document.activeElement` can be `null`, at least in IE while the page is initially loading. You're right in that it should be a non-issue if `search.focus()` does its job, though.

> `search.el.contains(activeEl)` should always be true as you're calling `search.focus()`

True based on the application-level view of things but that is dependent on the current function of the various components being pieced together. It may be over-cautious but it certainly isn't invalid.

\*shrugs\*

Like I said, I'm fine with changing whatever makes this get merged.  :stuck_out_tongue: