3.1.0

fixed user related issues:

• #34 submitted by @JanMoritzMeyer
• #35 submitted by @Mastermori
• #36 submitted by @loetmann

Instances:

• added a fallback Model (Webuntis\Models\Account) to get rid of the model not found error
• added option to set a default user model

Models:

• with the option ignore_children, the children of a Model will not be rendered, the values will only be arrays or ids then