Merge pull request #830 from gavlyukovskiy/patch-1

fixed throwing RuntimeException instead of JsonIOException

gson/src/main/java/com/google/gson/Gson.java

@@ -679,7 +679,7 @@ public void toJson(JsonElement jsonElement, Appendable writer) throws JsonIOExce
       JsonWriter jsonWriter = newJsonWriter(Streams.writerForAppendable(writer));
       toJson(jsonElement, jsonWriter);
     } catch (IOException e) {
-      throw new RuntimeException(e);
+      throw new JsonIOException(e);
     }
   }