Respect babel "ignore" option

[monovertex]

In Babel 7 the ignore option is no longer valid for @babel/preset-env, so there is currently no way of providing this option through ember-cli-babel.

I followed #158, which added sourceMaps option forwarding - this PR is pretty much the same.

Food for thought: should this plugin maybe allow the user to specify options separately for babel and for the env preset, instead of forwarding these manually? Since Babel separates them, it feels a bit weird that this plugin will bundle them together, even if it abstracts the env preset usage.

Fixes #305

[monovertex]

I'm not exactly sure why the Travis build fails 🤔

[houfeng0923]

ye, we need ignore. please

[houfeng0923]

@monovertex , if you use ember-auto-import , you can try skipBabel option .
i resolved my problem with it .

[monovertex]

We actually needed this behavior for internal files, but we realized after opening this PR that the files were not ignored with Babel 6 either, the ignore option was, well, ignored. The original intention was to not break some sensitive code that was already ES5 and lower compliant, but they were transpiled anyway and they worked in production for quite a while.

We also realized that ignore doesn't really make sense for internal files, because then you'd have to shim the module scaffolding.

I forgot about this PR, so I will close it now, seeing that this is not really needed.