Adding logo and rendering of logo (and credits in the README)
Method get_input_data() was changed to attribute input_data in PyMW
Making subject and predicate attributes "private"
Make Relationships Save Themselves

Refactored all the code of add_relationship into their respective
Relationship classes. This will be helpful later on when saving
relationships becomes more complicated.
Removing unused reference to node module
Adding a Membership Relationship and mining it from the Infobx Plugin