Support state filter for GetAllSprints call

* creates a GetAllSprintsOptions structure
* adds a new GetAllSprintsWithOptions method to accept an int boardID and new options structure
* adds filtering functionality to GetAllSprintsWithOptions method
* adds SprintsList type for handling pagination results data from GetAllSprints request
* updates tests

board_test.go

@@ -184,3 +184,35 @@ func TestBoardService_GetAllSprints(t *testing.T) {
 		t.Errorf("Expected 4 transitions. Got %d", len(sprints))
 	}
 }
+
+func TestBoardService_GetAllSprintsWithOptions(t *testing.T) {
+	setup()
+	defer teardown()
+
+	testAPIEndpoint := "/rest/agile/1.0/board/123/sprint"
+
+	raw, err := ioutil.ReadFile("./mocks/sprints_filtered.json")
+	if err != nil {
+		t.Error(err.Error())
+	}
+
+	testMux.HandleFunc(testAPIEndpoint, func(w http.ResponseWriter, r *http.Request) {
+		testMethod(t, r, "GET")
+		testRequestURL(t, r, testAPIEndpoint)
+		fmt.Fprint(w, string(raw))
+	})
+
+	sprints, _, err := testClient.Board.GetAllSprintsWithOptions(123, &GetAllSprintsOptions{State: "active,future"})
+
+	if err != nil {
+		t.Errorf("Got error: %v", err)
+	}
+
+	if sprints == nil {
+		t.Error("Expected sprint list. Got nil.")
+	}
+
+	if len(sprints.Values) != 1 {
+		t.Errorf("Expected 1 transition. Got %d", len(sprints.Values))
+	}
+}