startup perf: Reduce require() calls

Every require() that we do before the users sees UI reduces startup
time.

I used the following code (added to index.js) to log every require()
call in the main process:

```js
var Module = require('module')
var required = {}
Module.prototype.require = function (orig) {
  return function (id) {
    if (!required[id]) {
      required[id] = true
      console.log(`${id}   (from ${this.filename})`)
    }
    return orig.apply(this, arguments)
  }
}(Module.prototype.require)
```

From this I was able to learn that lots of modules were being required
that aren't actually used until later.

I also sent this related PR to eliminate another few require()s:
https://github.com/LinusU/node-application-config/pull/4

This increases startup time by 50ms.

We'll probably realize much bigger gains by following this same
procedure for the renderer process.

src/renderer/lib/state.js

@@ -181,19 +181,18 @@ function getExternalPlayerName () {
 }
 
 function load (cb) {
-  const state = getDefaultState()
-
   appConfig.read(function (err, saved) {
     if (err || !saved.version) {
       console.log('Missing config file: Creating new one')
-      setupStateSaved(onSaved)
+      setupStateSaved(onSavedState)
     } else {
-      onSaved(null, saved)
+      onSavedState(null, saved)
     }
   })
 
-  function onSaved (err, saved) {
+  function onSavedState (err, saved) {
     if (err) return cb(err)
+    const state = getDefaultState()
     state.saved = saved
     migrations.run(state)
     cb(null, state)