make order of precedence in setting environment know in docs, and consider changing

[toddzebert]

Given the line current(make(process.env.NODE_ENV || argv.env || "development")); if NODE_ENV is set to anything truthy it'll use that regardless of any other method (as the or is short-circuited) of setting the environment, and otherwise it'll fall to arg.env in the same way, and so forth. Make this clear in the documentation. Also, if NODE_ENV is set to "development" then not even gulp.task('set-prod', production.task); or environments.current(production); will override it

Plus, I think it should be reversed, command line should override NODE_ENV or code, and code should override NODE_ENV.

Thanks for the module!

[calvinjuarez]

I'm adding my voice here to note that now, in 2019, I'd also like the command line argument to take priority over an environment variable.

I disagree that code should be overridden by command-line argument. I think code should probably be the strongest, personally. But in any case, it's absolutely weird that environment variable wins.

[calvinjuarez]

With precedence now listed in the README, this is probably ready to close.

[toddzebert]

I haven't used this package in years so I'm probably not a good choice to decide if my original issue is still an issue or not.