Allowing to pass floating numbers

[fcamblor]

Currently, when we issue a iou @user 12.34 bot complains.

This PR provides support for decimal amount

IMPORTANT note : the change makes previously stored notes incompatible with the new ones as I keep storing amount as number (I only multiply/divide this value by 100, making previously stored values incompatible with new ones)

To be 100% accurate, I would have to provide a migration mongo script to multiply previous notes' amount by 100, but I don't have enough knowledge into mongoose to know if this is easily possible or not.

[mjlescano]

Hi @fcamblor! Thanks for this :)

But, there's no need to do the Float hack, because the schema type is already Number and mongoose supports float values.