Fix the build, add new pre-commit hook

I have commented out the code that broke the build (there is still issue when we are publishing tests and artifacts to gh-pages branch - I need to fix that in the future).

I have added new pre-commit plugin.

I have notice that we are not running test properly.. in [karma config file](https://github.com/cam-technologies/time-booker/blob/master/client/test/config/karma.conf.js#L48) we run tests only against 'client/src/app/app.js' instead of 'client/src/**/*.js'.. this mean our coverage is incorrect so we should have look on this in the future