Add organization id to the provider.

Use the change in nytm/go-grafana-api#62 to
apply an organization id to the provider.

Usage might look like this:

```hcl
provider "grafana" {
  url = "someurl"
  auth = "adminuser:somepass"
}

resource "grafana_organization" "neworg" {
  name = "neworg"
  admin = "neworgadmin"
}

provider "grafana" {
  alias = "neworg"
  url = "someurl"
  auth = "neworgadmin:somepass"
  org_id = grafana_organization.neworg.org_id
}

resource "grafana_data_source" "neworg_graphite" {
  provider = grafana.neworg
  type = "graphite"
  name = "neworg-graphite"
}
```

Author: medains

grafana/provider.go

@@ -24,6 +24,12 @@ func Provider() terraform.ResourceProvider {
 				DefaultFunc: schema.EnvDefaultFunc("GRAFANA_AUTH", nil),
 				Description: "Credentials for accessing the Grafana API.",
 			},
+			"org_id": {
+				Type:        schema.TypeInt,
+				Required:    true,
+				DefaultFunc: schema.EnvDefaultFunc("GRAFANA_ORG_ID", 1),
+				Description: "Organization id for resources",
+			},
 		},
 
 		ResourcesMap: map[string]*schema.Resource{
@@ -42,6 +48,7 @@ func providerConfigure(d *schema.ResourceData) (interface{}, error) {
 	client, err := gapi.New(
 		d.Get("auth").(string),
 		d.Get("url").(string),
+		d.Get("org_id").(int),
 	)
 	if err != nil {
 		return nil, err

website/docs/index.html.markdown

@@ -22,6 +22,10 @@ The provider configuration block accepts the following arguments:
   are provided in a single string and separated by a colon. May alternatively
   be set via the ``GRAFANA_AUTH`` environment variable.
 
+* org_id - (Required) The organization id to operate on within grafana.
+  Default org_id is 1.  May alternatively be set via the
+  GRAFANA_ORG_ID environment variable.
+
 Use the navigation to the left to read about the available resources.
 
 ## Example Usage
@@ -30,6 +34,7 @@ Use the navigation to the left to read about the available resources.
 provider "grafana" {
   url  = "http://grafana.example.com/"
   auth = "1234abcd"
+  org_id = 1
 }
 
 resource "grafana_dashboard" "metrics" {