Fix Thor's deprecation error

[udaykadaboina]

Thor 1.0.0(CHANGELOG) has deprecated the behavior of relying on default exit_on_failure? Hence, making the devs define this method.

Thor #621, #625

PRIOR TO CHANGE:

bundle exec derailed exec perf:mem_over_time development
ERROR: "derailed exec" was called with arguments ["perf:mem_over_time", "development"]
Usage: "derailed exec"
Deprecation warning: Thor exit with status 0 on errors. To keep this behavior, you must define `exit_on_failure?` in `DerailedBenchmarkCLI`
You can silence deprecations warning by setting the environment variable THOR_SILENCE_DEPRECATION.

AFTER:

bundle exec derailed exec perf:mem_over_time development
ERROR: "derailed exec" was called with arguments ["perf:mem_over_time", "development"]
Usage: "derailed exec"

[schneems]

Hi, thanks for the PR this looks great. Can you add a changelog entry and then rebase? https://www.codetriage.com/rebase

[udaykadaboina]

Hi @schneems let me know how it looks.

[schneems]

Thanks!