Use eventSource.resource for gcal events.

Populate resources with events coming from google calendars,
for example :
```
resources: [
  {name: "Calendrier 1", id:"c1"},
  {name: "Calendrier 2", id:"c2"}
]
,
eventSources: [
  {url: "https://www.google.com/calendar/feeds/idxx/basic", resource:"c1"},
  {url: "https://www.google.com/calendar/feeds/idyy/basic", resource:"c2"}
]
```

This fixes #15