Add --ignore-tags CLI option.

Add CLI option to not count scenarios with certain tags when grouping by steps.  For example:  --ignore-tags "@(WIP|Draft|Manual)"

Test results:

rspec spec/
...........................................................................*...................................*..........................................................................

Pending:
  ParallelTests::RSpec::FailuresLogger should not log examples without location
    # Temporarily disabled with xit
    # ./spec/parallel_tests/rspec/failure_logger_spec.rb:75
  ParallelTests::RSpec::SummaryLogger prints failing examples
    # Temporarily disabled with xit
    # ./spec/parallel_tests/rspec/summary_logger_spec.rb:12

Finished in 1 minute 8.02 seconds
186 examples, 0 failures, 2 pending

real	1m9.435s
user	1m25.554s
sys	0m8.186s