on_view_created: pass pipe info
fix missing arg to create_destination

create_destination does not take window as an argument; this is in turn
done by storing the window.
build output is pinnable

For "last", viewport was used instead of visible_region()/show() because
the latter seemed a little unreliable (scrolling was off).
allow user to provide default scroll setting
scroll to top only once

Scrolling on each update screws with manual scrolling.
fix AttributeError on last_scroll_region for first run
'last scroll' is done in timeout

Scrolling seems off when done immediately; probably due to view not yet
getting updated. Scrolling in a timeout seems to get around this.

Again visible_region()/show() seemed off.
describe pipe_views, hacking notes
Merge branch 'scroll-pin'

Fixes #2.

Conflicts:
	pipe_views.py