Updated initiation object method with class methods

[khoroshevskyi]

Fixed:

• Change from_dict() and from_pandas() from instance method to class method. #443
• Make a peppy.Project from a sample yaml file #458
• Env variables in config file are not expanding #464
• Add docs how to use new init methods
• Make additional methods from_csv, from_config ... and print deprecation in the old version
• Add better example from_dict: a) to_dict -> from_dict b) create dict and then use function from_dict
• add actual url in docs
• Remove yacman from dependencies