use Bundler's solution to the environment problem

[VinceGuidry]

Bundler has three methods to clear out it's changes to the environment: Bundler.with_original_env, Bundler.with_clean_env, and Bundler.with_unbundled_env. I think with_original_env would most closely match the expectations of someone running a helper script rather than a completely clean one or one modified by re. Though, now that I think about it, with_unbundled_env would allow us to pass information along to the helpers.

Edit: reading the code says with_clean_env is the same as with_unbundled_env.
https://docs.ruby-lang.org/en/master/Bundler.html#method-c-with_original_env