babel-preset-env: `DEBUG` option

Using targets:
{
  "chrome": "52",
  "firefox": "50",
  "ie": "11"
}

Using modules transform: commonjs

Using plugins:
  check-es2015-constants { "firefox":"50", "ie":"11" }
  transform-es2015-arrow-functions { "ie":"11" }
  transform-es2015-block-scoping { "firefox":"50", "ie":"11" }
  transform-es2015-classes { "ie":"11" }
  transform-es2015-computed-properties { "ie":"11" }
  transform-es2015-destructuring { "firefox":"50", "ie":"11" }
  transform-es2015-duplicate-keys { "ie":"11" }
  transform-es2015-for-of { "firefox":"50", "ie":"11" }
  transform-es2015-function-name { "firefox":"50", "ie":"11" }
  transform-es2015-literals { "firefox":"50", "ie":"11" }
  transform-es2015-object-super { "ie":"11" }
  transform-es2015-parameters { "firefox":"50", "ie":"11" }
  transform-es2015-shorthand-properties { "ie":"11" }
  transform-es2015-spread { "ie":"11" }
  transform-es2015-sticky-regex { "ie":"11" }
  transform-es2015-template-literals { "ie":"11" }
  transform-es2015-typeof-symbol { "ie":"11" }
  transform-es2015-unicode-regex { "ie":"11" }
  transform-regenerator { "firefox":"50", "ie":"11" }
  transform-exponentiation-operator { "firefox":"50", "ie":"11" }
  transform-async-to-generator { "chrome":"52", "firefox":"50", "ie":"11" }
  syntax-trailing-function-commas { "chrome":"52", "firefox":"50", "ie":"11" }

Using polyfills with `usage` option:

[src/in.js] Based on your code and targets, none were added.
src/in.js -> lib/in.js

[src/in2.js] Based on your code and targets, none were added.
src/in2.js -> lib/in2.js