make filename extension lowercase. fixes a compile error.
minor typesetting fixes
add illustration of ellipse fitting.

TODO: This lab needs solutions.
workaround for displaying a single russian character.
Added rank approximation figures
Add figure to Laplace problem.

Added more explanation to some problems.
Reworded a problem
Added a note to profiling problem.
changed figures for matplotlib lab

added figures.py
Merge pull request #219 from ayr0/exposition

Expositions to labs.