Streamlined QA tools

- Removed coveralls (service does not work)
- Replaced check-cs.sh with inline `--config-file` option for php-cs-fixer
- Removed psr0 php-cs-fixer rule (we use psr4)
- Added contribution guide
CS fixes (unused use statements, control spaces)
Merge branch 'feature/streamline-tools'

Streamline QA tools and add contribution guide