Change name of "context" to "environment"

[stevvooe]

This will make it much easier to understand code the involves context.Context and the thing that manipulates the local filesystem.

[kzys]

+1

@AkihiroSuda @dmcgowan Thoughts?

[dmcgowan]

Yes, although the root package hasn't been touched in awhile. If you have plans to resurrect some of the work here, it is worth discussing and looking at some of the old designs and work.

[kzys]

Sure. I already took a few easy ones (such as #190 and #191) but may check other issues.

Does it have design docs somewhere?