Add initial producer code

include/cppkafka/buffer.h

@@ -0,0 +1,28 @@
+#ifndef CPPKAFKA_BUFFER_H
+#define CPPKAFKA_BUFFER_H
+
+namespace cppkafka {
+
+class Buffer {
+public:
+    using DataType = unsigned char;
+
+    Buffer();
+    Buffer(const std::string& data);
+    Buffer(const DataType* data, size_t size);
+
+    Buffer(const Buffer&) = delete;
+    Buffer(Buffer&&) = delete;
+    Buffer& operator=(const Buffer&) = delete;
+    Buffer& operator=(Buffer&&) = delete;
+
+    const DataType* get_data() const;
+    size_t get_size() const;
+private:
+    const unsigned char* data_;
+    size_t size_;
+};
+
+} // cppkafka
+
+#endif // CPPKAFKA_BUFFER_H