title: Insert event with Google Calendar API in Chrome Extension keeps failing
body: <p>I'm having trouble getting the format right for a chrome extension using the Google Calendar API.  I have an OAuth2 access token (which is valid, I can test that with tokenInfo), but am having trouble.  I'm using a proprietary framework to build the extension, which complicates things, but maybe you could help me find out what information I'm missing:</p>
  
  <pre><code>var eventParams = e.data,
      request = {
        'method' : 'POST',
        'async'  : true,
        'url':   'https://www.googleapis.com/calendar/v3/calendars/'+CAL_ID + '/events',
        'headers': {
          'Authorization' : TOKEN
        },
        'params': eventParams
      };
  </code></pre>
  
  <p>My token looks like this:</p>
  
  <pre><code>{↵ "issued_to": "831101123055-874tukfvuvkma6s0l7m70iqlc3lirnkc.apps.googleusercontent.com",↵ "audience": "831101123055-874tukfvuvkma6s0l7m70iqlc3lirnkc.apps.googleusercontent.com",↵ "scope": "https://www.googleapis.com/auth/calendar",↵ "expires_in": 3600,↵ "access_type": "offline"↵}
  </code></pre>
  
  <p>The error I'm getting is:</p>
  
  <pre><code>{
   "error": {
    "errors": [
     {
      "domain": "usageLimits",
      "reason": "dailyLimitExceededUnreg",
      "message": "Daily Limit for Unauthenticated Use Exceeded. Continued use requires signup.",
      "extendedHelp": "https://code.google.com/apis/console"
     }
    ],
    "code": 403,
    "message": "Daily Limit for Unauthenticated Use Exceeded. Continued use requires signup."
   }
  }
  </code></pre>
  
  <p>I'm not really sure why that's the case, because my request is authenticated.  Am I not passing the token correctly?  Someone has suggested that I need to include an API key, but my understanding is that API keys are only for apps requiring public access and don't need access to user data, and that OAuth2 takes the place of an API key.</p>
  
  <p>I'd appreciate any help you guys can offer!  Thank you!</p>