Include code checkers

It would be nice to integrate some static code checkers into the CI. Some tools to look into could be:

• cppcheck http://cppcheck.sourceforge.net/
• krazy http://www.englishbreakfastnetwork.org/krazy
• vera++ http://www.inspirel.com/vera/
• cpplint https://google.github.io/styleguide/cppguide.html

In particular, this maybe could be used to enforce some code style as well.