Fix Travis memory utilization:

Split the websocket read test to reduce compile time memory usage
by a small amount, which ought to be enough to let it compile in
a constrained environment like Travis.

Signed-off-by: Damian Jarek <damian.jarek93@gmail.com>

include/boost/beast/websocket/stream.hpp

@@ -123,7 +123,8 @@ class stream
     friend class close_test;
     friend class frame_test;
     friend class ping_test;
-    friend class read_test;
+    friend class read1_test;
+    friend class read2_test;
     friend class stream_test;
     friend class write_test;