standardized error handling

[EricFalkenberg]

standardize error handling for all of the following methods

• from_json()
• from_dict()
• from_file()
• to_json()
• to_dict()

Behavior

• if value is of incorrect type it should always raise a type error
• if dictionary contains a key that is not in the packson object, the function should raise an attribute error
• the to_* methods should raise serialization errors if something in the object cannot be serialized