Bumping thor to minor 1.4 due to CVE

[crsantos]

What

Due to thor's CVE and this .gemspec being specified to patch it's impossible to bump thor's version.
(original issue).

Also dependabot failed to bump thor in this repo:

Bonus

• Forced to bump guard to a more recent version.
• Took the change to update .ruby-version - it should be supported on circleci

This fixes #208.

References

rails/thor#897

Next steps

• Let me know if I should revert the bump to 0.37.2 or keep it
• Confirm that tests pass with current ruby versionn

[ashfurrow]

This is great, thank you! I ran the tests locally and I like the version bump 👍