Fix detection for Opera Mini
Fix detection for Opera Mini

Opera Mini v7 doesn’t support `placeholder` although its DOM seems to indicate so. To work around this, there’s no other way than UA sniffing, sadly :(

Fixes #173. Closes #130.

zsh2938/jquery-placeholder,mlms13/jquery-placeholder,mlms13/jquery-placeholder,jeremy-hawes/jquery-placeholder,7213/jquery-placeholder,7213/jquery-placeholder,jeremy-hawes/jquery-placeholder,fashionsun/jquery-placeholder,mathiasbynens/jquery-placeholder,mathiasbynens/jquery-placeholder,SimenB/jquery-placeholder,zsh2938/jquery-placeholder,SimenB/jquery-placeholder,fashionsun/jquery-placeholder