* Update to Faraday v2

Faraday 2 has been out for a year and is the recommended version to
use by the community now. This change updates the dependency to Faraday
2 and drops the middleware bundle since it is incompatible.

This change has one regression, but it's a regression for the state of
the world as it was in 2012. Back then, it was pretty common for APIs to
respond to JSON requests with `text/javascript` or
`application/javascript` for their Content-Type, which was incorrect.
Faraday Middleware contains a kludge to paper over that fact, which you
can see [in the source][1].

Faraday 2 drops this kludge because most APIs are well-behaved now with
respect to Content-Type. This introduces a minor regression in
Bridgetown in the event that someone has a preexisting site that queries
one of these misbehaved APIs.

[1]: https://github.com/lostisland/faraday_middleware/blob/e68ff84470705c8a59d9aa99b98cb36101fa10ad/lib/faraday_middleware/response/parse_json.rb#L16-L44



* Update old blog posts to reflect Faraday 2

Since we're updating to Faraday 2, these blog posts should reflect how
to do it in the current version instead of the old version. We might not
want to make this change until releasing 1.3, though.

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Co-authored-by: Jared White <jared@whitefusion.studio>