Support Mapnik 3 in install docs

[pnorman]

There are no known major Mapnik 3 issues left.

After merging, I'll have a look at the issues against the Mapnik 3 milestone. Those which will require Mapnik 3 style features can be left, but others can be closed.

[matkoniecz]

#1579 is closed but "Text is farther away from lines" and "maxzoom depreciated and will be removed in 4.x spams the log(...)" are not marked as solved. First problem is in the section "Major issues".

Also, it seems that according to mapnik/mapnik#2913 we still need add vertical-alignment:middle to labels on lines using offsets.

[pnorman]

#1579 is closed but "Text is farther away from lines" and "maxzoom depreciated and will be removed in 4.x spams the log(...)" are not marked as solved. First problem is in the section "Major issues".

I don't plan to fix the max/min zoom stuff anytime soon, because it's a minor issue.

When I last did a review, I couldn't see any other problems.

[matthijsmelissen]

I have been exclusively using Mapnik 3 in Kosmtik for a couple of months, and I haven't encountered any issues.

What would be the next step? Are we ready to recommend the server admins to move to Mapnik 3?

[gravitystorm]

Sounds great to me. I've opened a ticket at openstreetmap/chef#39

This should allow us to "fix" various text-rendering issues. I'm also happy to require mapnik3 at any point - we'll just need to bump the version number when we start using mapnik3-only features.

[matthijsmelissen]

Just to be clear, I haven't tested exhaustively on possible Mapnik 3 issues - I just haven't encountered any while doing development.

So I guess we shouldn't be too surprised if some issues pop up anyway.

[gravitystorm]

Don't worry, I carefully hedged my statement on that issue :-)