reorganized files and added usage paragraph to readme

tests/fuzzer.c

@@ -0,0 +1,33 @@
+#include <assert.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <ctype.h>
+#include "xjson.h"
+
+__AFL_FUZZ_INIT();
+
+int main()
+{
+
+#ifdef __AFL_HAVE_MANUAL_CONTROL
+  __AFL_INIT();
+#endif
+
+    unsigned char *buf = __AFL_FUZZ_TESTCASE_BUF; // must be after __AFL_INIT
+                                                  // and before __AFL_LOOP!
+    char pool[65536];
+    xj_error  error;
+
+    while(__AFL_LOOP(10000)) 
+    {
+        int len = __AFL_FUZZ_TESTCASE_LEN;
+
+        xj_alloc *alloc = xj_alloc_using(pool, sizeof(pool), 4096, NULL);
+        assert(alloc != NULL);
+        
+        xj_decode(buf, len, alloc, &error);
+        
+        xj_alloc_del(alloc);
+    }
+    return 0;
+}