Refine the parsing of response status line; add UT for utility.

webcc/utility.h

@@ -7,9 +7,10 @@ namespace webcc {
 
 std::string RandomUuid();
 
-// Split a string to two parts by the given token.
-bool Split2(const std::string& str, char token, std::string* part1,
-            std::string* part2);
+// Split a key-value string.
+// E.g., split "Connection: Keep-Alive".
+bool SplitKV(const std::string& str, char delimiter,
+             std::string* key, std::string* value);
 
 }  // namespace webcc