Add the option to use path-style S3 URLs.

[grampajoe]

It's sometimes desirable to use path-style URLs over virtual-host-style URLs. For example, a bucket name with a dot in it will trigger invalid SSL certificate errors on some browsers, since S3's *.s3.amazonaws.com certificate only covers single-level subdomains.

This adds the S3_URL_STYLE setting, which can be one of 'host' or 'path', defaulting to 'host' for compatibility.

[e-dard]

Thanks. Probably going to take a while to look at this, since there are a couple of PRs on the go at the moment, which you may need to rebase from if they're merged. 😄

[e-dard]

any thoughts on this, @eriktaubeneck ?

[eriktaubeneck]

It looks clean to me. I'm not sure I completely understand the motivation, but I don't think it overcomplicates anything.

[grampajoe]

Yeah, my example was kind of unclear.

Say you have a bucket called all.the.things. If you use a host-style URL, that's all.the.things.s3.amazonaws.com/<key>, which needs its own SSL cert since it won't be covered by the one Amazon provides for *.s3.amazonaws.com. You can avoid having to pay for that by using a path-style url, s3.amazonaws.com/all.the.things/<key>, instead.

[eriktaubeneck]

This should take care of #20 then as well. @e-dard do you want to merge this in?