Added Alex's extension for sheet 3
Added Alex's solution for sheet 2 and the code for sheet 3
Added lecture 5
Changes made in the determinant code
More changes made in the determinant code
Changes in the polytopality range finder code
More changes in the determinant code
More changes in the polytopality range finder code
Merge branch 'master' of https://github.com/alex-alvarez/discrete-geometry-lecture-notes into alex-alvarez-master
Merge branch 'alex-alvarez-master'

Conflicts:
	2013/coding/dag2013-alex-alvarez/apps/polytope/src/direct_sum.cc
Merge remote-tracking branch 'origin/master'