use alphanumeric QR and elm qr module

lib/admin/pairing.js

@@ -2,10 +2,14 @@ const fs = require('fs')
 const pify = require('pify')
 const readFile = pify(fs.readFile)
 const crypto = require('crypto')
+const baseX = require('base-x')
 
 const options = require('../options')
 const db = require('../db')
 
+const ALPHA_BASE = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:'
+const bsAlpha = baseX(ALPHA_BASE)
+
 function unpair (deviceId) {
   const sql = 'update devices set paired=FALSE where device_id=$1'
 
@@ -31,7 +35,7 @@ function totem (hostname, name) {
     const sql = 'insert into pairing_tokens (token, name) values ($1, $3), ($2, $3)'
 
     return db.none(sql, [hexToken, caHexToken, name])
-    .then(() => buf.toString('base64'))
+    .then(() => bsAlpha.encode(buf))
   })
 }