* Update singly_linked_list.py
printing current.data rather than node address in __repr__ for a more readable print statement
* eval(repr(c)) == c
The output of `__repr__()` _should look like a valid Python expression that could be used to recreate an object with the same value_.
https://docs.python.org/3.4/reference/datamodel.html#object.__repr__
* += --> +
* Improved Singly Linked List
Added String Representations of Nodes and Linked Lists
Added support for indexing and changing of Node data using indices.
* Added a few comments to Linked Lists
* Reformatted to conform to PEP8
* Added from_sequence.py
Convert a Python List to Linked List comprising of Nodes and return head.
* Added print_reverse.py
Recursive program to print the elements of a Linked List in reverse.
* Change 'is not None' for more Pythonicness
