renamed slideOutToleft to slideOutToLeft

I was listing all ionic animations and I found that at lines [76] and [80] in [scss/_animations.scss] it was written `slideOutToleft` instead of `slideOutToLeft`.
You can fix it directly without this pull request, I did it only to show the right lines,
thanks :) 

[76]: https://github.com/driftyco/ionic/blob/master/scss/_animations.scss#L76
[80]: https://github.com/driftyco/ionic/blob/master/scss/_animations.scss#L80
[scss/_animations.scss]: https://github.com/driftyco/ionic/blob/master/scss/_animations.scss