Fix focus issue

You could

* focus replace box and enter replacement
* hit enter in replace box to do the replacement
* it would focus the find box

Frustrating, but fixed.
Fix current-result 

It was no longer highlighting the current find result
Make selection on search result highlight that result.

This was broken by the react editor not emitting the dom event for 
selection changes.

refs #232
Fix error with FindResultsView attachment and update on react editor

When you’d split-open a file, the react editor wasn’t attached or 
rendered yet. So there was no under layer, and when you’d try to request
a display update, it would call functions on objects that weren’t there.

So I hack this with a delay. This is not a pretty fix. It will all go 
away when there are marker views in core.

refs #232
Fix pane destruction issue

* open fnr
* run a search
* split a file
* close the split
* no more search markers ever!

When a pane was destroyed, it would remove the .search-results node
with it. This would call the FindResultsView.unsubscribe() fn which 
would unsubscribe it from all marker changes. 

refs #232
Attach FindResultsView when the active pane item changes
Merge pull request #235 from atom/bo-tues-fixes

Fixes for use with React editor