Changed Emitter::size() to return std::size_t instead of unsigned

include/yaml-cpp/emitter.h

@@ -30,7 +30,7 @@ namespace YAML
 		
 		// output
 		const char *c_str() const;
-		unsigned size() const;
+        std::size_t size() const;
 		
 		// state checking
 		bool good() const;

src/emitter.cpp

@@ -24,7 +24,7 @@ namespace YAML
 		return m_stream.str();
 	}
 	
-	unsigned Emitter::size() const
+    std::size_t Emitter::size() const
 	{
 		return m_stream.pos();
 	}