require.context

I'm creating this issue to unify the discussions about `require.context`.

While that's very handy to import components, it comes with some drawbacks like #130, #113 and https://github.com/diegohaz/arc/issues/128#issuecomment-281914665

Personally, I don't have problems with it, the advantages are bigger than the issues for me. But, as many are having problems, we should consider removing it by default or at least give proper instructions on how to remove it.

If you are using this webpack feature (whether your project is based on ARc or not), please share your thoughts.

Start by reading the linked discussions in #130, #113, and the referenced comment about require.context. Determine whether the project should remove this webpack feature by default or document how to remove it; done requires a decided direction, not just more opinions.

Written by the indexing model from the issue text.