Return the Meta on error

Previously, this would never actually return the Meta data structure
since by the time that it got parsed, we already knew that the request
was good.  Now, we do a special parse when we know that it failed so
that we can return the structured data (in particular, we want to be
able to use the HTTP status code).

client.go

@@ -3,7 +3,6 @@ package groupme
 import (
 	"bytes"
 	"encoding/json"
-	"fmt"
 	"io/ioutil"
 	"net/http"
 )
@@ -77,7 +76,14 @@ func (c Client) do(req *http.Request, i interface{}) error {
 
 	// Check Status Code is 1XX or 2XX
 	if getResp.StatusCode/100 > 2 {
-		return fmt.Errorf("%s: %s", getResp.Status, string(bytes))
+		resp := newJSONResponse(nil)
+		if err := json.Unmarshal(bytes, &resp); err != nil {
+			// We couldn't parse the output.  Oh well; generate the appropriate error type anyway.
+			return &Meta{
+				Code: HTTPStatusCode(getResp.StatusCode),
+			}
+		}
+		return &resp.Meta
 	}
 
 	if i == nil {
@@ -89,11 +95,6 @@ func (c Client) do(req *http.Request, i interface{}) error {
 		return err
 	}
 
-	// Check Status Code is 1XX or 2XX
-	if resp.Meta.Code/100 > 2 {
-		return &resp.Meta
-	}
-
 	return nil
 }