big refactoring, wip.
register only once mouse/touch event.
added note to README.md.
re-enable all tests.
notifies the last drag event.
handle tests cursor pos correctly.
fixed multiple targets for drag.
fixed wrong target for end drag event.
Merge branch 'fix/drag' into develop
test - check different targets b/w start & end.
ensure start & end targets are the same.
bump version to 0.0.8.