Test against node v0.10, v4, and v6

[springmeyer]

No description provided.

[coveralls]

Coverage remained the same at 97.685% when pulling ccb0568 on node-v4-6-test into d9a0bdc on master.

[springmeyer]

Hmm, failing with:

not ok 230 round-tripped mbtiles are approx. the same size
  ---
    operator: ok
    expected: true
    actual:   false
    at: Put.makeAssertions (/home/travis/build/mapbox/tilelive/test/stream-deserialize.test.js:189:11)
  ...

[springmeyer]

Looks like this has been failing for a while. I notice as far back as #188

[springmeyer]

Don't have time to look into this test failure now, punting on this. Anyone please feel free to pick this up.

[mapsam]

@springmeyer I put this together yesterday in a separate PR: #195 - I didn't include node v0.10 though.

[springmeyer]

Thanks @mapsam - sorry for missing your PR! Closing this one.