multiple stacks of simpleToasts

Hello,
I have made a slight change to the simply-toast so that it allows multiple stacks of messages - based on the appendTo option. You can have - for example - one stack of toasts appended to the "body" element, and one stack appended to a settings window, or one stack for each row of a table etc..

best regards
Jan Sourek

![st-shot](https://cloud.githubusercontent.com/assets/3274187/5488809/050b9dea-86c3-11e4-8562-9e1d914a1107.jpg)