Updated README to notify users of Dart SDK version requirements.
BUG=
R=kevmoo@google.com, zra@google.com
Review-Url: https://codereview.chromium.org/2832013003 .
diff --git a/README.md b/README.md
index 59379b1..346085b 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,11 @@
Dart Synchronous HTTP Client
============================
+**Important Note:** This package requires the RawSynchronousSocket class to
+work, which should become available in version 1.24 of the Dart SDK. If you
+really want to use this package now, you'll have to build the Dart VM from
+the most up-to-date source hosted in dart-lang/sdk.
+
A simple Dart HTTP client implemented using RawSynchronousSockets to allow for
synchronous HTTP requests.
