Improved beast::http::message:

* Add headers::erase
* Set http::message version with std::pair
* Use std::pair for headers::value_type

beast/http/tests/parser.test.cpp

@@ -58,9 +58,19 @@ public:
         log << "|" << result.first.headers["Field"] << "|";
     }
 
+    void
+    test_headers()
+    {
+        headers h;
+        h.append("Field", "Value");
+        expect (h.erase("Field") == 1);
+    }
+
     void
     run()
     {
+        test_headers();
+
         {
             std::string const text =
                 "GET / HTTP/1.1\r\n"