Add W3C Caveat to Browser Support Info (#412)

README.md

@@ -30,7 +30,7 @@ Changelog
 Browser Support
 ---------------
 
-All current browsers are fully supported.
+All current browsers are fully* supported.
 
 * Firefox 7-9 (Old) (Protocol Version 8)
 * Firefox 10+ (Protocol Version 13)
@@ -39,6 +39,8 @@ All current browsers are fully supported.
 * Internet Explorer 10+ (Protocol Version 13)
 * Safari 6+ (Protocol Version 13)
 
+(Not all W3C WebSocket features are supported by browsers. More info in the [Full API documentation](docs/index.md))
+
 Benchmarks
 ----------
 There are some basic benchmarking sections in the Autobahn test suite.  I've put up a [benchmark page](http://theturtle32.github.com/WebSocket-Node/benchmarks/) that shows the results from the Autobahn tests run against AutobahnServer 0.4.10, WebSocket-Node 1.0.2, WebSocket-Node 1.0.4, and ws 0.3.4.