move encoding/mvt from tegola

[ear7h]

This is two commits, the first is just a plain cut-over and the the second is some minor changes to the the ScaleGeo function.

Also, the mvt package depends on github.com/golang/protobuf/proto and based on previous discussions I did not vendor it since this is a library. Is this correct?

[gdey]

That is correct. Did you update the README

[gdey]

Also, please rebase to the lastest version of master

[coveralls]

Pull Request Test Coverage Report for Build 231

• 227 of 617 (36.79%) changed or added relevant lines in 4 files are covered.
• 9 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-1.9%) to 60.243%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
encoding/mvt/tile.go	0	32	0.0%
encoding/mvt/prepare.go	16	75	21.33%
encoding/mvt/layer.go	55	118	46.61%
encoding/mvt/feature.go	156	392	39.8%
<!--	Total:	227	617	36.79%	-->

Files with Coverage Reduction	New Missed Lines	%
planar/triangulate/constraineddelaunay/triangulator.go	9	57.78%
<!--	Total:	9		-->

Totals
Change from base Build 219:	-1.9%
Covered Lines:	5258
Relevant Lines:	8728

---

💛 - Coveralls

[ear7h]

• @gdey your requests for the var block caused an issue with typing... I'm not sure if my approach is correct check 2e1bb2c
• I left debugging in for future users

[ARolek]

@ear7h the only addition I would suggest is a quick README.md to the mvt package demonstrating how to use it.