Give a type to the _batch list (#62)
The comment and lack of type signal that this would be a list of objects
matching the `parameters` argument to `sendRequest`, but what is added
to this map is the full request which is always a `Map`.
diff --git a/lib/src/client.dart b/lib/src/client.dart
index 1e421ed..f52f630 100644
--- a/lib/src/client.dart
+++ b/lib/src/client.dart
@@ -24,8 +24,8 @@
/// The current batch of requests to be sent together.
///
- /// Each element is a JSON-serializable object.
- List _batch;
+ /// Each element is a JSON RPC spec compliant message.
+ List<Map<String, dynamic>> _batch;
/// The map of request ids to pending requests.
final _pendingRequests = <int, _Request>{};
