catch more corrupted data
Merge branch 'master' into 'master'

Master

found some more possible errors in the input data to catch
Add makefile option for NDEBUG.
Merge https://github.com/mattmilten/appfs
Purge warning.
Merge https://github.com/mattmilten/appfs
Update README.md
Merge branch 'master-gitlab'
Adds exercise 6 plus the solution.
Merge pull request #43 from AndreG-P/master

Adds exercise 6 plus the solution.
Merge https://github.com/mattmilten/appfs
Update README.md
Initial gitignore. Ignores coverage data.
Merge https://github.com/mattmilten/appfs
Update README.md
Advanced gitignore.
Merge pull request #46 from wuschel91/master

Add gitignore stuff mentioned in issue #44
Some minor improvements