fix ruby-version file
add jquery-nestable and implement draggable pages
first draft of update pagetree method
add rspec binstubs
implement serverside pagetree update
Revert "add rspec binstubs"

This reverts commit 06225cd26413b68f3662fede89c3ad313beefe16.
fix specs
update changelog
update changelog
extend readme (image size config is mandatory)
bump version