Let slide(index) default to preset speed
Let slide(index) default to preset speed

I would expect the slide method to use the default speed if none was
passed to the function. Added that functionality.

nickleefly/swipe,d5-css/Swipe,leeleo26/Swipe,huzion/Swipe,d5-css/Swipe,yizhicheng/Swipe,jonnywyatt/Swipe,wklc2015/Swipe-1,loup-brun/swipe,EugenAz/swipe,arcxyz/swipe-add-partial,jinlong/Swipe,Mexiswow/Swipe,iwanttotellyou/Swipe,arcxyz/swipe-add-partial,DemocraciaEnRed/swipe,zycFran/Swipe,rmoszczynski/Swipe,krisdigital/Swipe,mengqing723/Swipe,thebird/Swipe,srjkv13/Swipe,DemocraciaEnRed/swipe,miaotmac/swipe,prashen/Swipe,houyulei/Swipe,lyfeyaj/swipe,srjkv13/Swipe,GerHobbelt/Swipe,eonezhang/Swipe,tilfab/Swipe,nickleefly/swipe,EugenAz/swipe,miaotmac/swipe,jonnywyatt/Swipe,mengqing723/Swipe,micheledurante/Swipe,tilfab/Swipe,wklc2015/Swipe-1,fancyboynet/Swipe,Mexiswow/Swipe,Luobata/Swipe-,thebird/Swipe,suniaoo/scale-swipe,prashen/Swipe,leeleo26/Swipe,yizhicheng/Swipe,fancyboynet/Swipe,iwanttotellyou/Swipe,zycFran/Swipe,eonezhang/Swipe,krisdigital/Swipe,suniaoo/scale-swipe,voronianski/swipe-js-iso,huzion/Swipe,lyfeyaj/swipe,loup-brun/swipe,voronianski/swipe-js-iso,jinlong/Swipe,GerHobbelt/Swipe