Enforce single-quotes in Rubocop

[dunkOnIT]

If anyone else wants to pick this up, it requires the following in .rubocop.yml:

Style/StringLiterals:
  Enabled: true

And then running rubocop -a to deal with any instances where that rule hasn't been enforced.

I'll try do it later today/on Monday

[misaka]

PR created as above, it seems like there isn't enough appetite for this, at the moment at least. Happy to contribute further if this changes.

[dunkOnIT]

Yeah unfortunately the risk/reward of trying to go about these changes it too high for the team's capacity at the moment.

If you're interested in contributing on other issues, let me know and I'd be happy to point out some other good first issues!