move config.startTime to app.startTime

This also captures the true start time since it runs before any
require() calls, so the time to require() will be taken into account.

main/config.js

@@ -2,6 +2,5 @@ var path = require('path')
 
 module.exports = {
   APP_NAME: 'WebTorrent',
-  INDEX: 'file://' + path.resolve(__dirname, '..', 'renderer', 'index.html'),
-  startTime: Date.now()
+  INDEX: 'file://' + path.resolve(__dirname, '..', 'renderer', 'index.html')
 }