The core package accepts a babelrc option, which if set to false stops
the transforms from using .babelrc and .babelignore files. Document
this option and remove the --no-babelrc CLI flag, referring to the CLI
documentation instead.
[skip ci]
Just a minor fix. I'm new to Babel's API and this tripped me up. Seems like it happened to others before (e.g. #2859). Guessing this came from an earlier `var babel = require('babel-core')` which does work.