Vendor upstream URL parsing to simplify internal config

[kylebarron]

Because url has deferred parsing in the object_store builders, we need to special-case url handling. Naturally, passing url to a store with with_url means that object_store doesn't actually parse the URL until the build() method, and at that point we can no longer access config information from the built AmazonS3. Without special-casing this URL handling, pickling would fail for instances created from from_url.

Therefore, we handle this by vendoring the small amount of URL parsing from upstream. So we apply the URL parsing onto our config HashMaps and then apply those to the builder. So our configs and those used by the raw stores stay in sync.

We originally stored the url separately, but that meant that the bucket name was stored in up to three different places (bucket variable, in the url, and in the config). This simplifies the internal config by ensuring we only store each piece of config data in only one place.