deliteful/Toaster widget

` _nonRemovableAreOnlyPersistents` is the best (also the worst) name I could come up with. Please feel free to suggest anything. This test is basically testing this method which relies on `m._tobeRemoved` and `m.isExpirable()` booleans to output a result.

In the toaster, there is a list of messages. Inside, some messages have expired and need to be removed, so they are marked with `m._tobeRemoved == true`. The rest have `m._tobeRemoved == false`, either because 
- they haven't expired yet so we need to wait a little more, or
- they never will (those I call a persistent, they have `duration` set to -1 they stay there forever unless the user discards them).

The behavior of the Toaster differs depending on whether the messages that can't be removed are:
- a mix of persistent and expirable messages, in case which ` _nonRemovableAreOnlyPersistents`  returns `false`
- all persistent, it returns `true`.

In the first case, each "tobeRemoved" message is kept in the DOM at its initial positions, visibility set to none, until all the other messages expire (see picture one), then it flushes the list. That prevents the messages from moving around which could be hard on the eye.

<img width="200px" src="https://cloud.githubusercontent.com/assets/2982512/3255861/52c0ad34-f210-11e3-84b8-57d74ef367f8.gif">

In the second case, there are only persistant messages, so all tobeRemoved messages are removed from the DOM. This is because we don't want to keep holes in the pile forever so we sort of "condense" the list.

<img width="200px" src="https://cloud.githubusercontent.com/assets/2982512/3255860/4fe41bd2-f210-11e3-931b-0d4961bf1ce5.gif">   

I hope this clarifies what i'm trying to do in this test.