refactor logging
add few info logs
make `wait_for` more DRY
merge frame control methods in a single `frame(child)`
add a debug log when a file is choosen
fix `display` argument that now correctly call `show` method
`sleep` method now has a default value
ensure we process application events while showing the webview
add a debug log when showing the webview
fix reply content handling that no more uses cache

inspired by
https://github.com/balrok/Ghost.py/commit/2b5e2492dcefd5d6d541ec946aded68f577a2e04
ensure we process events after page load
fix version handling
capture only renders the given region (as oposed to rendering the whole page then then cutting round the image

Conflicts:
	ghost/ghost.py
fix alert handling that is now per instance
fix confirm handling that is now per instance
fix prompt handling that is now per instance
`prompt` and `confirm` can now receive both a value or a callable returning a value
move CI to drone.io
add doc title
add installation notes