Fixed ByteArrayInputStream.peek implementation (previous one could lead to unexpected behavior on skip(n))

Author: shyiko

src/main/java/com/github/shyiko/mysql/binlog/io/ByteArrayInputStream.java

@@ -163,7 +163,9 @@ public int available() throws IOException {
     }
 
     public int peek() throws IOException {
-        this.peek = readWithinBlockBoundaries();
+        if (peek == null) {
+            peek = readWithinBlockBoundaries();
+        }
         return peek;
     }