v0.2.0

• properly handle not enough data error when waiting for the first header byte
• peek on network in example
• make buffer type void* and allocate memory with malloc in example
• remove unsigned modifiers (potential bitmap errors)
• added varnum helpers
• support multiple subscriptions in single packets for subscribe and unsubscribe
• fix potential integer overflows by using enough sized signed types
• added docs about buffer sizes and the use of the int type
• check suback codes and return error if a subscription has been denied