Keybase Installer errors out on old versions of node -- add a version check?

Hi!

I'm just setting up keybase for the first time, and unfortunately the very first thing I saw on running the installer was this:

~ $ keybase-installer

/usr/local/lib/node_modules/keybase-installer/node_modules/gpg-wrapper/node_modules/iced-spawn/lib/stream.js:5
unction ctor() { this.constructor = child; } ctor.prototype = parent.prototype
^
TypeError: Cannot read property 'prototype' of undefined
at __extends (/usr/local/lib/node_modules/keybase-installer/node_modules/gpg-wrapper/node_modules/iced-spawn/lib/stream.js:5:199)
at /usr/local/lib/node_modules/keybase-installer/node_modules/gpg-wrapper/node_modules/iced-spawn/lib/stream.js:10:5
at Object. (/usr/local/lib/node_modules/keybase-installer/node_modules/gpg-wrapper/node_modules/iced-spawn/lib/stream.js:23:5)
at Object. (/usr/local/lib/node_modules/keybase-installer/node_modules/gpg-wrapper/node_modules/iced-spawn/lib/stream.js:120:4)
at Module._compile (module.js:449:26)
at Object.Module._extensions..js (module.js:467:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.require (module.js:362:17)
at require (module.js:378:17)

At the time I had an old version of node installed (v0.8.18), once I upgraded I saw a friendlier error message telling me to install the GPG Suite.

I don't care much that I had to upgrade node, but it would have been nice to have a friendly error message. The rest of keybase seems generally pretty friendly.

Start with the keybase-installer command and reproduce the failure using Node v0.8.18, then inspect the installer’s startup and version handling. Done means an unsupported Node version produces a friendly actionable error instead of the raw TypeError; verify the behavior with the reported old version and a supported version.

Written by the indexing model from the issue text.