added rubocop gem to help follow Ruby style guide
rubocop: added newlines at end of files, use && and ||
code refactoring according to rubocop
added license_finder gem
small style changes
small changes according to Ruby Style Guide and rubocop
aded copyright-header gem
simplified get_data method of many sources
ALM-657 simplified calculation of event_metrics
reorganized SourceHelper module into three smaller concerns
ALM-657 reorganized tests for background tasks, small test fixes
ALM-657 added more rspec test coverage for concerns
simplified the rspec tests for sources a bit by using subject
ALM-657 fine-tuned rspec tests for changes in background jobs