Fix unsafe raw SQL warning

[flackou]

Starting from Rails 5.2, there's a deprecation warning on using raw SQL fragments in some AR methods, including order, cf Rails 5.2 changelog :

Require raw SQL fragments to be explicitly marked when used in relation query methods.

The warning precises :

Non-attribute arguments will be disallowed in Rails 6.0

We just need to wrap the SQL in Arel.sql(...) to remove the warning. Tests config is also fixed for Rails >= 4 (fixing #129).

[coveralls]

Coverage increased (+35.6%) to 84.364% when pulling f69b4091a680beb453136e44888caa3bab20e474 on flackou:fix_unsafe_raw_sql_warning into 9e5251afb76f14a5a2cd975023f0a0fab1e0cc80 on geokit:master.

[coveralls]

Coverage increased (+35.6%) to 84.364% when pulling 6448e9a0ef5cb72b1190ebfa175d7aba380ab6b8 on flackou:fix_unsafe_raw_sql_warning into 9e5251afb76f14a5a2cd975023f0a0fab1e0cc80 on geokit:master.

[mnoack]

Thanks for the PR @flackou

[nholden]

Thanks so much for this one, @flackou and @mnoack!

I'd love to see a new release of the geokit-rails gem with this included so that we can silence the deprecation warning in our Rails 5.2 apps without needing to point our Gemfiles at master. Let me know if there's anything I can do to help out with that.

[mnoack]

@nholden @flackou - I've just released a gem for the latest code. I've also added ruby 2.4/rails 5 to the travis test suite.

[nholden]

Thanks so much, @mnoack! Works great. 🎉