Change how scope attribute is accessed via config mixin

[zacholade]

class ConfigMixin(object):
    @property
    def config(self):
        """
        Returns the bots config.py file
        """
        return __import__('config')

    @property
    def scope(self):
        """
        Returns a string representation of the scopes
        """
        return " ".join(self.config.scope)

Ideally self.config.scope Currently: self.scope and this is for all cogs....