feat(config): instrumenter override option

Enable fine-tuning which preprocessor should be used for which files
Add README.md section
Add tests
Update existing tests to comply with new dependency requirement
Merge branch 'instrumenter-option' of github.com:gvarsanyi/karma-coverage into gvarsanyi-instrumenter-option

Conflicts:
	package.json
Merge branch 'gvarsanyi-instrumenter-option'