Hash in DashDependency does not take class name into account

[hhoeflin]

In

https://github.com/plotly/dash/blob/e727dd7e37d20147f6eefbdd35bd12319a026b27/dash/dependencies.py#L27

the hash is implemented as

def __hash__(self):
    hash(str(self))

where

def __str__(self):
    return "{}.{}".format(self.component_id_str(), self.component_property)

def __repr__(self):
    return "<{} `{}`>".format(self.__class__.__name__, self)

so that an Input and State with the same id would yield the same hash-value.

I plan to insert Input and State objects into a dict, and this could cause issues.

[alexcjohnson]

Good catch @hhoeflin - let's change that to hash(repr(self))