Use object itself as parametter for callback

Merge pull request #8 from ryuran/fix/20minutes/offsetTop

change parammetter for callback function

Fix jump stuck/unstuck posdates limit

Merge pull request #7 from ryuran/fix/20minutes/offsetTop

avoir enable usage if already enabled

First minor release

seems stable

Fix some issue and rework

• delete checkVisibility dependency.

initial tag

Merge pull request #4 from ryuran/fix/20minutes/offsetTop

fix offsetTop