Clarification/grammar edits to linked list section
Heaps: fixed root removal description, minor edits
BSTs: further explanation of insert method
Hints and minor edits to hash tables section
remove forced figure location

wrap some tikz graphics in figures.
remove balanced trees

This has been moved to the lecture portion of the course.
Summarized balanced tree in two sentences.
revisions to linked lists

1. Always inherit from object in code we give to students!
2. Circularly-linked is not important enough to talk about.
3. Avoid reusing variable names (like counter).  self.counter vs counter
can be confusing.
4. Use the proper class functions when possible (__len__ for example).
5. Removed complexity jargon.  Replaced with scale of very efficient,
efficient, and very inefficent.
revise trees

1. Removed heaps.  We don't have time to talk about them.
revise hash tables

1. Shorten many of the explanations in hashtables.  Replaced exposition
with concrete examples where possible.
2. Removed section on sparse matrices
revise hash table problem

consolidate the review of hash tables into one problem.
final edits

1. remove code for doubly-linked list since we never use it or reference
it again.
Merge pull request #691 from ayr0/mg_datastructures

Data Structures