WebSocket ping, fixes, coverage:

* Improve test coverage
* tests for invokable in composed ops

* Update documentation
* Add License badge to README
* Target Windows 7 SDK and later
* Make role_type private
* Remove extra unused masking functions
* Allow stream reuse / reconnect after failure
* Restructure logic of composed operations
* Allow 0 for read_message_max meaning no limit
* Respect keep alive when building HTTP responses
* Check version in upgrade request
* Response with 426 status on unsupported WebSocket version
* Remove unnecessary Sec-WebSocket-Key in HTTP responses
* Rename to mask_buffer_size

* Remove maybe_throw
* Add ping, async_ping, async_on_pong
* Add ping_op
* Add pong_op
* Fix crash in accept_op
* Fix suspend in close_op
* Fix read_frame_op logic
* Fix crash in read_op
* Fix races in echo sync and async echo servers

test/websocket/detail/stream_base.cpp

@@ -0,0 +1,40 @@
+//
+// Copyright (c) 2013-2016 Vinnie Falco (vinnie dot falco at gmail dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+// Test that header file is self-contained.
+#include <beast/websocket/detail/stream_base.hpp>
+
+#include <beast/unit_test/suite.hpp>
+#include <initializer_list>
+#include <climits>
+
+namespace beast {
+namespace websocket {
+namespace detail {
+
+class stream_base_test : public beast::unit_test::suite
+{
+public:
+    void testClamp()
+    {
+        expect(detail::clamp(
+            std::numeric_limits<std::uint64_t>::max()) ==
+                std::numeric_limits<std::size_t>::max());
+    }
+
+    void run() override
+    {
+        testClamp();
+    }
+};
+
+BEAST_DEFINE_TESTSUITE(stream_base,websocket,beast);
+
+} // detail
+} // websocket
+} // beast
+