Sign atom.exe with mapbox signing cert. Refs #828.
[publish sign-atom]
Remove bak file [publish sign-atom]
Changelog entry
Update to mapnik-omnivore@1.3.13
Update changelog. [skip ci]
Merge pull request #845 from mapbox/omnivore-1313

mapnik-omnivore@1.3.13
Merge branch 'mb-pages' into sign-atom [skip ci]

Conflicts:
	CHANGELOG.md
Merge pull request #838 from mapbox/sign-atom

Sign atom.exe
Merge branch 'mb-pages' into saveCenter