Bump debug from 0.7.4 to 2.6.9

Bumps [debug](https://github.com/visionmedia/debug) from 0.7.4 to 2.6.9.
- [Release notes](https://github.com/visionmedia/debug/releases)
- [Changelog](https://github.com/visionmedia/debug/blob/2.6.9/CHANGELOG.md)
- [Commits](debug-js/debug@0.7.4...2.6.9)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package-lock.json

@@ -11,7 +11,7 @@
     "cookie-parser": "~1.0.1",
     "coordtransform": "^2.1.2",
     "d3": "^4.12.2",
-    "debug": "~0.7.4",
+    "debug": "~2.6.9",
     "express": "~4.0.0",
     "fnv-plus": "^1.2.12",
     "grunt-cli": "^1.2.0",