Refactor LinkedList() and Node() to improve pythonicity
Update Queue()with the new attribute name of the next node in a linked list
Refactor LinkedList.size() by reducing the number of lines and return statements to make it more pythonic.
Refactor Queue() by improving readability and pythonicity
Refactor Stack() and Data() to be more readable and pythonic
Refactor Heap() to improve readability & pythonicity

Method names are more explicit, class docstring spaced in accordance with PEP 257, unused method removed
Refactor test_pop_reorganizes()

Removed unnecessary lines in test_pop_reoganizes; reformated test numbers
Add PQNode.__unicode__() and PriorityQ.__unicode__()
Improve pythonicity and readability

Remove unnecessary lines from tests related to PriorityQ.pop(), standardize import order, uppercase constants
Improve pythonicity and readability of Graph()

Add docstrings to all public methods. Change Graph.nodes() and Graph.edges() to return a list that copies the related attributes rather than returning the attributes themselves to prevent manipulation of the nodes and edges outside of the add_ and del_ methods
Update tests to account for changes in Graph()

Update test_nodes_empty() and test_edges_empty() to expect an empty list instead of an empty set
Refactor Graph() for more consistant use of sets

Update methods to always refer to ._nodes and ._edges when using 'in' rather than the list returned from .nodes() and .edges() to take advantage of O(1) lookup.
Add negative tests for methods that raise errors
Merge pull request #24 from jefrailey/simple_graph

Simple graph