Experiment with deferring org-mode in search buffers

As mentioned in #4, it might be possible to not activate org-mode inside new buffers unless matches are found. If so, that might provide a significant speed boost. The question is probably whether the outline-related functions still work in a plain or text-mode buffer. If not, something would have to basically reimplement them, which would seem to violate a lot of DRY/NIH/etc. We shall see.

Thanks to @zeltak for your help. Will report here when I have something ready to test.