Example fixes (#96)

* Add example for kafka buffered producer

* Add notes regarding bool returned in produce failure callback

* Fix example names

examples/producer_example.cpp

@@ -0,0 +1,78 @@
+#include <stdexcept>
+#include <iostream>
+#include <boost/program_options.hpp>
+#include "cppkafka/producer.h"
+#include "cppkafka/configuration.h"
+
+using std::string;
+using std::exception;
+using std::getline;
+using std::cin;
+using std::cout;
+using std::endl;
+
+using cppkafka::Producer;
+using cppkafka::Configuration;
+using cppkafka::Topic;
+using cppkafka::MessageBuilder;
+
+namespace po = boost::program_options;
+
+int main(int argc, char* argv[]) {
+    string brokers;
+    string topic_name;
+    int partition_value = -1;
+
+    po::options_description options("Options");
+    options.add_options()
+        ("help,h",      "produce this help message")
+        ("brokers,b",   po::value<string>(&brokers)->required(), 
+                        "the kafka broker list")
+        ("topic,t",     po::value<string>(&topic_name)->required(),
+                        "the topic in which to write to")
+        ("partition,p", po::value<int>(&partition_value),
+                        "the partition to write into (unassigned if not provided)")
+        ;
+
+    po::variables_map vm;
+
+    try {
+        po::store(po::command_line_parser(argc, argv).options(options).run(), vm);
+        po::notify(vm);
+    }
+    catch (exception& ex) {
+        cout << "Error parsing options: " << ex.what() << endl;
+        cout << endl;
+        cout << options << endl;
+        return 1;
+    }
+
+    // Create a message builder for this topic
+    MessageBuilder builder(topic_name);
+
+    // Get the partition we want to write to. If no partition is provided, this will be
+    // an unassigned one
+    if (partition_value != -1) {
+        builder.partition(partition_value);
+    }
+
+    // Construct the configuration
+    Configuration config = {
+        { "metadata.broker.list", brokers }
+    };
+
+    // Create the producer
+    Producer producer(config);
+
+    cout << "Producing messages into topic " << topic_name << endl;
+
+    // Now read lines and write them into kafka
+    string line;
+    while (getline(cin, line)) {
+        // Set the payload on this builder
+        builder.payload(line);
+
+        // Actually produce the message we've built
+        producer.produce(builder);
+    }
+}