Grafana upgrade 3.0.4 (#76)

Dashboards *system-metrics.json* and *welcome.json* were removed because they cause an error when loaded

**UI**
```
Dashboard init failed
Template variables could not be initialized: b.metricFindQuery is not a function
```

**JS Console**

```
TypeError: b.metricFindQuery is not a function
    at updateOptionsFromMetricFindQuery (boot.16792590.js:10)
    at b (boot.16792590.js:40)
    at h (boot.16792590.js:35)
    at boot.16792590.js:35
    at n.$eval (boot.16792590.js:35)
    at n.$digest (boot.16792590.js:35)
    at boot.16792590.js:35
    at e (boot.16792590.js:34)
    at boot.16792590.js:34
```

Dashboard *docker.json* was modified by removing id. Client cannot provide an id when POST-ing a new dashboard - there is rather unhelpful error message

```
HTTP/1.1 404 Not Found
{"message":"Dashboard not found","status":"not-found"}
```

Dockerfile

@@ -46,7 +46,7 @@ RUN     git clone https://github.com/etsy/statsd.git /src/statsd
 # Install Grafana
 RUN     mkdir /src/grafana                                                                                    &&\
         mkdir /opt/grafana                                                                                    &&\
-        wget https://grafanarel.s3.amazonaws.com/builds/grafana-2.1.3.linux-x64.tar.gz -O /src/grafana.tar.gz &&\
+        wget https://grafanarel.s3.amazonaws.com/builds/grafana-3.0.4-1464167696.linux-x64.tar.gz -O /src/grafana.tar.gz &&\
         tar -xzf /src/grafana.tar.gz -C /opt/grafana --strip-components=1                                     &&\
         rm /src/grafana.tar.gz
 

grafana/dashboards/docker.json

@@ -1,5 +1,5 @@
 {
-  "id": 4,
+  "id": null,
   "title": "Docker",
   "originalTitle": "Docker",
   "tags": [],