message: Update to latest prebuildify + use ~ ranges for dependencies
diff: "abstract-leveldown": "~6.0.0",
  "bindings": "~1.3.0",
  "fast-future": "~1.0.2",
  - "napi-macros": "^1.8.1",
  - "node-gyp-build": "^3.5.1"
  + "napi-macros": "~1.8.1",
  + "node-gyp-build": "~3.7.0"
  },
  "devDependencies": {
  "async": "^2.0.1",
  "node-gyp": "^3.8.0",
  "nyc": "^12.0.2",
  "optimist": "~0.6.1",
  - "prebuildify": "ralphtheninja/prebuildify",
  + "prebuildify": "^2.10.0",
  "prebuildify-ci": "^1.0.4",
  "readfiletree": "~0.0.1",
  "rimraf": "^2.6.1",
  