Fix info severity

[mdix]

When the report contains vuln of type info, the detail & install reporters fail because ther's no info property in the severityColors object in utils.js. This issue was undiscovered because all fixtures had info: 0.

Use the following commits to reproduce locally with my fork
failing test
eb9d01b
implementation fixing it
4476b94

[welwood08]

I was accidentally re-implementing a lot of what you've already done in several PRs here without checking first. So my time wasn't all wasted, I have a suggestion for this PR in particular. In lib/utils.js:

 function severityLabel (sev, withColor, bold) {
+  if (!(sev in severityColors)) return sev.charAt(0).toUpperCase() + sev.substr(1).toLowerCase()

This way it never crashes in the future if any unknown severity is added to the API's output.

[zkat]

yay. This is a good find! Thanks for catching this <3