BubbleWrap 1.5.0

- Add `BubbleWrap.use_weak_callbacks=(true/false)`, to support `Proc#weak!`
- Add `Camera.popover_from` to show the photo picker on iPad
- Add `Camera.available?`
- Add `UIView#when_screen_edge_panned` gesture shortcut
- Allow #observe to default the first argument to `self` (to observe changes on the same object)
- Fix HTTP connections to run in common run loop modes
- Fix multipart HTTP connections to use `Content-Disposition: attachment`