Bump eris from 0.14.1 to 0.15.1

Bumps [eris](https://github.com/abalabahaha/eris) from 0.14.1 to 0.15.1.
- [Release notes](https://github.com/abalabahaha/eris/releases)
- [Commits](https://github.com/abalabahaha/eris/compare/0.14.1...0.15.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -5,7 +5,7 @@
   "dependencies": {
     "body-parser": "^1.18.3",
     "ejs": "^3.1.2",
-    "eris": "^0.14.0",
+    "eris": "^0.15.1",
     "express": "^4.16.4",
     "formidable": "^1.2.1",
     "fs-extra": "^9.0.0",