Where does keybase get installed?

I tried to install keybase using the installer. It seems to install fine, but it doesn't tell me where it got installed so I don't know where the executable is.

```
15:43 warp@bullet-bill:~/usr$ npm install keybase-installer
npm http GET https://registry.npmjs.org/keybase-installer
npm http 304 https://registry.npmjs.org/keybase-installer
keybase-installer@0.1.21 node_modules/keybase-installer
15:43 warp@bullet-bill:~/usr$ node_modules/.bin/keybase-installer
info: Made temporary directory: /tmp/keybase_install_71tbSM1E6oB3ukwg4fj0kQ
info: Using keyset version v1
info: Fetching URL https://dist.keybase.io/sig/files/1/index.asc
info: Fetching URL https://dist.keybase.io/pkg/stable
Download /pkg/files/keybase-0.2.21.tgz [=================================================] 100% 0.0s (3509475 bytes total)
info: Fetching URL https://dist.keybase.io/sig/files/1/keybase-0.2.21.tgz.asc
info: verified signature of keybase-0.2.21.tgz against keybase-0.2.21.tgz.asc
info: Running npm install keybase-0.2.21.tgz: this may take a minute, please be patient
=====================================================================

Welcome to keybase.io!

You have now successfully installed the command-line client. If you're new to the
service run:

$ keybase signup # signup for a new account
$ keybase push # to push your public key to the server
-- or --
$ keybase gen # generate a new key and push it

If you already signed up via the Web or another keybase client, try:

$ keybase login # establish a session with the server, and pull down keys

Once you're configured, you can:

$ keybase prove twitter # prove your twitter identity
$ keybase id max # to identify a friend
$ keybase track max # to track them and write a proof to the server

And then attempt crypto actions like enc/dec/verify/sign. See `keybase --help` for
more details.

info: cleaning up tmpdir /tmp/keybase_install_71tbSM1E6oB3ukwg4fj0kQ
15:44 warp@bullet-bill:~/usr$ keybase
keybase: command not found
```

Start by reproducing the npm install keybase-installer flow through node_modules/.bin/keybase-installer and inspect the installer output and installation location it reports. Done means the installer clearly identifies where the keybase executable was installed, so the user can invoke it or update PATH accordingly.

Written by the indexing model from the issue text.