Tailwindcss debug environment variable

[r-sierra]

Hi, this PR adds an environment variable to generate non-minified assets as discussed in #400

[flavorjones]

Thank you for drafting this! I'd like to simplify the environment variable check, and I'm not sure what to do if both the rake task argument is passed and the environment variable is set.

[r-sierra]

Hi @flavorjones, thanks for taking the time to review this changes. This is ready for another review.

[flavorjones]

I rebased and made a small change from unless ENV[].nil? to if ENV.key?(). This looks great! Will merge when it goes green.

Thank you!