Revert "Remove solutions so we can merge with master"

This reverts commit 6d9759c19999588f05abb8754791e09dcd18ffd6.
Add solution snippets
Merge pull request #13 from scikit-image/solutions

Solutions for sections 0, 1, and 2
Fix README file
Add readme file
Tweak readme
Add solutions to 00, 3, 4, adv0, and adv1
Merge pull request #14 from jni/soln

Add solutions to 00, 3, 4, adv0, and adv1