Upgrade dependencies

npm audit gives
```
found 46 vulnerabilities (21 low, 19 moderate, 5 high, 1 critical) in 6373 scanned packages
39 vulnerabilities require semver-major dependency updates.
7 vulnerabilities require manual review. See the full report for details.
```

The one critical vulnerability is
```
Critical Command Injection
Package growl
Dependency of mocha [dev]
Path mocha > growl
More info https://nodesecurity.io/advisories/146
```
This requires growl to be greater than version 1.10.2, which requires mocha to be at least 4.0.1. Currently mocha 3.1.2 is being used.

Start by running npm audit and reviewing the reported mocha > growl dependency path, including the advisory details. Determine which of the listed vulnerabilities can be resolved through dependency updates and which require manual review; done means the critical issue and the broader audit findings have been addressed or documented.

索引モデルが issue の本文から書いたものです。