Remove ignored child nodes in tree

[MarkvanMents]

Helps to resolve memory issues such as #185 by removing child nodes from nodes where ignoreTagAttribute (data-proofer-ignore) is set.
This reduces the amount of memory needed by htmltest if large sections of documents (such as generated tables of contents) can be ignored. See linked issue for the use case.

(This PR will not be supported by Mendix, but is on a Mendix fork so it can be used on their own documentation site)

[MarkvanMents]

Hi Will, @wjdp
Wondered if you had had time to look at this PR. We discussed it on issue #185.
(I have implemented it on our site and it seems to be working fine there).
I realise that you probably have other things to do, and I can continue to use my own build in the meantime, so there is no urgency.
Thanks
Mark

[wjdp]

Thanks for the understanding @MarkvanMents I'll have a play around with this branch but looks good!

FYI the broken test isn't you and was fixed in 8d8ff25

[MarkvanMents]

Hi Will,
Just wondered if you are still maintaining this repo.
I have applied this change to our fork, so we don't run out of memory on our Travis build, but would really like to go back to getting the version in your repo if we can.
It would be a shame if this project died, as we are finding the results from htmltest very fast and useful. But, of course, I understand that this is not your main focus. I would offer to help, but the change in this pull request is stretching my knowledge of Go 😀
In any case, thanks for putting your work into GitHub and sharing it.

[wjdp]

Hey @MarkvanMents I am still maintaining this repo, but currently it's more of a periodic thing than continuous. Seems I didn't merge this last time I did, sorry! I'll sit down and go through PRs soon!

[MarkvanMents]

Hi Will (@wjdp )
Just checking in to find out how things are going.
I'm afraid there is a conflict now, but looks like it is easy to resolve, so I'll do it. But it will need testing again.
Yours
Mark