Ignoring late packets and fixing qbuf references

[danielquinn]

This is sort of a loaded PR because there was a mixup in merging the "late" packets issue. I thought that was already in master, but I guess not :-(

Anyway, there's 3 things in here of note:

• Traceroutes can sometimes have "late" packets which, currently should be considered bogus. In future, that's going to change though and this code will have to be firmware version away and perform shuffling for later versions. For now though, we just ignore these packets.
• Issue qbuf issue #56, a failure to capture qbuf data is fixed here too. Basically the problem was that some DNS results are a single result, while others are result-sets, and the qbuf is placed in totally different places in each case. We now account for this.
• A documentation update. Better formatting, and importing of the newly-renamed CHANGES.rst and newly-minted CONTRIBUTING.rst into the wider docs.

Closes #56.

[astrikos]

I am wondering if we can have only on contrib file for the 3 projects since they can be basically the same. Is there a way to have it in one of them and them have a link for the other projects.

[danielquinn]

I had the same thinking, but I don't know. I believe there's something in Sphinx about "inter-sphinx" documentation, and rtfd also has some sort of method to allow interlinking, but I have no experience with it.

Maybe create this as an issue and one of us can look into it?