Move to the format we actually intend for the manifest and lock

[sdboyer]

I think there's general agreement among us four that JSON is not what we want to use. I know that @freeformz and I both lean TOML. But we're gonna have to do this, and probably sooner rather than later.

Unfortunately, there's a wrinkle: one of the major arguments for using YAML or TOML over JSON is that both of those formats support comments, and JSON does not. However, neither BurntSushi/toml nor go-yaml/yaml appear to support encoding comments. idk about other implementations, but...well, that really sucks. (This knowledge courtesy of the cockroachdb folks, reporting it about glide: Masterminds/glide#691)

I don't know where that leaves us, but the clock is ticking.

[sdboyer]

so, I feel like the thing to do about this is...once we open up this repo, we basically put out a note saying, "hey, if some awesome Gopher wants to get support for proper comment handling into one of these encoding libs by X date, then we'll use it. otherwise, we'll have to stick with JSON"

[sdboyer]

closing in favor of #119