Ref-style link definition syntax: COLON missing?

[tin-pot]

Nice work, and a useful idea to collect guidelines like this!

One issue though: I think the examples for definitions of reference-style links, like for example:

[id2]     http://long-url.com

(line 1611 ff) are missing the ":" after the "]", and thus should read instead:

[id2]:     http://long-url.com

At least that's what Gruber's and the CommonMark rules require, if I see this right.

[cirosantilli]

Thanks!