Update to turf 3.0

[wboykinm]

From v2.0.2. Will require some function updates, and some expansion of aggregation tools in turf.meta().

[mapsam]

Hey @wboykinm! Now that Travis tests are running smoothly again, I'd say updating Turf to 3.x would be a great next step. Please take a stab if you're interested!

It would be really awesome to reduce the size of our turf dependency by only requiring the turf functions that we use, instead of the whole library.

[wboykinm]

@mapsam Thanks! Will give it a shot. resumes epic battle with gulp

[wboykinm]

All good here.

[mapsam]

Excellent work @wboykinm - thanks for taking this on!