Adding "trackingPosition" for 1.9

[alex-humphreys]

Without trackingPosition in the NBT, 1.9 will always show a green arrow in the center of the map.

[alex-humphreys]

Frames on the left have trackingPosition set to 0. Frames on the right are straight from the tool; Minecraft 1.9 automatically sets trackingPosition to 1.

I'm unclear as to why the build failed.

[alex-humphreys]

(did some more research) This occurs specifically in my case because xCenter/zCenter is set to 0,0 and my item frames are also within the vicinity of 0,0.

During your testing, it's reasonable to assume that this was not tested near 0,0.

Alternatively, you can set xCenter and zCenter arbitrarily high (999999) to achieve essentially the same effect, although this seems more jank/"hacky".

[djfun]

Thanks for sending in a pull request. The CI tests fail at the moment, because of the changed contents of the map file. If you change line 50 of tests/mocha/test-server.js to:
expect(body).to.equal('7b886d0e7b9a4caa02c6d343555ecdd6bdea8495');
the tests should run without error.
I confirmed the created map file to work in minecraft 1.9 as well as 1.8 so I will merge this, once the tests are fixed.