Fixed issue #25. Depend on psr/log "~1.0" and update dev dependencies.
Merge commit '78ebe0d3a9bc6019371bb769280822d6646ef6a6' into feature/25-psr-log-semver

Conflicts:
	composer.lock
Merge pull request #27 from simplesamlphp/feature/25-psr-log-semver

Fixed issue #25. Depend on psr/log "~1.0" and update dev dependencies.