Fix some errors in header files.

include/stream/stream.hpp

@@ -7,6 +7,8 @@
  *
  */
 
+#pragma once
+
 #include <algorithm>
 #include <utility>
 #include <functional>

include/stream/streams/streams.hpp

@@ -17,8 +17,6 @@
     return *this; \
   }
 
-std::map<void*, bool> data;
-
 namespace stream {
 #define STREAM_ITERATOR_COPY() \
   copy(other.copy), dereference(other.dereference), compare(other.compare), destroy(other.destroy), advance(other.advance), type_(other.type_)