Add default option on head requests

[supremebeing7]

This attempts to resolve #345. I'm pretty confident the code works, but I couldn't get the spec figured out. I left my attempt in there, with the expectation line commented out.

Suggestions welcome/encouraged.

[jnunemaker]

I'm not comfortable merging without a passing spec and I don't have time to look into this right now. If someone else could help, that would be great.

[supremebeing7]

Okay, I had some more time and was able to refactor this a bit to make it more easily testable, then add specs.

I went with the "principle of least surprise" approach outlined by xunker, ensuring that head requests maintain the HEAD method across all redirects, unless the user specifies maintain_method_across_redirects: false in the options.

[jnunemaker]

This means it will do a GET if it is set to false, is that right?

[supremebeing7]

Exactly. I wanted to make sure there was still a way to override the new behavior, in case someone wanted to do that.

[xunker]

@supremebeing7 Thanks for taking care of this, I'm glad my research was helpful to you. 👍

[supremebeing7]

@xunker Very helpful 🎉