[other] 確認custom URL Scheme ＆ 確認是否有裝某隻APP

http://peko.idv.tw/archives/2011/04/20/784/

http://stackoverflow.com/questions/627916/iphone-safari-check-if-url-scheme-is-supported-in-javascript/1404662#1404662

有點土砲

不過卻很實在！