Create run_test.sh that will run tests for a single exercise
Create run_test.sh that will run tests for a single exercise

Make it easy for learners to run the tests for a single exercise.
Otherwise, calling

    ruby exercises_spec.rb

would run all the tests, producing error output for exercises we haven't
even written yet. This allows us to run the appropriate tests as needed.

teddywing/Beginning-Ruby-Exercises,teddywing/Beginning-Ruby-Exercises