replace anyhow with std error and an type alias

[softprops]

Issue #229, if available:

Description of changes:

Replaced anyhow with std::error::Error type alias.

also renamed some lambda-http examples. cargo warns that when you have to crates with examples with the same name, collisions ensue. I gave these unique names

By submitting this pull request

• I confirm that my contribution is made under the terms of the Apache 2.0 license.
• I confirm that I've made a best effort attempt to update all relevant documentation.

[davidbarsky]

Thanks for doing this. I'm not sure the alias should be re-exported from the main runtime. If I recall correctly, the type alias can be private to the crate but used in public bounds without issue. I think I would prefer that, but what do you think?

[softprops]

I can do pub (crate). The idea behind making it pub was do abbreviate the api a bit. I'd be happy to defer to that later if it becomes too onerous to type out in each lambda.

[softprops]

Done, hindsight in that last commit is that is a very laborious process to update code references when this type changes. In most ideal cases though it won't change so that's maybe something we don't have to optimize for now.

[davidbarsky]

Yeah, it’ll probably be a pain, but not exporting avoids a future compatibility issue.

[davidbarsky]

Alright, I think this is good. I'll merge this in.