Just another meaningless work

It adopted metronome from cwilso:
- https://github.com/cwilso/metronome

Live demo:
- http://cornguo.atcity.org/test/kpdepon
- https://cornguo.github.io/kpdepon

Credits (by commit, newest first):
- adpot to applepig's template
- add test song, especially thanks to will1118@ptt
- add youtube player by suggestion of xx52002@ptt
- cleanup js by suggestion of applepig
- adjust animation by suggestion of horizondrift@ptt
- change page layout by suggestion of xx52002@ptt

Known problems:
- not fully working on IE/Edge
- not sure how to get precise timing in javascript
- mobile devices has tons of bugs, it just will work as-is
- if something's wrong, just let it go