fix doc & example transition opacity from .99 to 1

The initial thought was that an opacity animation from 0.01 to 1 causes trouble on some browser. But after testing on opera 12.15, ff 23, ie 10, chrome 30, desktop/mobile safari 7 and chrome android I confirm this works.
Merge pull request #460 from chenglou/opacity-1

fix doc & example transition opacity from .99 to 1