Fix some typos
Fix annotating when there are no marks

The code 'forgot' to return a value in this case.
Oops. Remove leftover debug code
Oops. Fix bad debug leftovers
Unfix the Makefile

This reverts commit d5c03cd6975309797c32ec6e853da319bd4f9ee7.

Fuck you, @Vladimiroff
Fixes on collection lecture

Add images and fix bad template parts
Update 02-collections.slim
Merge pull request #12 from GerganaPetrova/master

Fix some typos
Merge pull request #14 from stcakova/patch-4

Update 02-collections.slim