Added Convert Function as discussed on Issue#22

dataset_utils/Readme.md

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+# Dataset Utils
+
+This directory contains utility functions related to Datasets.
+
+Current Implemented features
+
+  * Convert CSV files to JSON([Issue](https://github.com/mlpack/models/issues/22))
+  * Convert CSV files to XML([Issue](https://github.com/mlpack/models/issues/22))

dataset_utils/convert.cpp

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+#include <iostream>
+#include <unordered_map>
+#include <boost/range/combine.hpp>
+#include <boost/lexical_cast.hpp>
+#include <boost/property_tree/ptree.hpp>
+#include <boost/property_tree/xml_parser.hpp>
+#include <boost/property_tree/json_parser.hpp>
+#include <boost/tokenizer.hpp>
+#include <string>
+#include <fstream>
+#include <unordered_map>
+
+
+using namespace boost::property_tree;
+using namespace boost;
+
+class Convert
+{
+  auto tokenize(std::string& line)
+  {
+    std::vector<std::string> col_names;
+    tokenizer<escaped_list_separator<char> > tk(line, escaped_list_separator<char>());
+    for (tokenizer<escaped_list_separator<char> >::iterator i(tk.begin()); i != tk.end(); ++i)
+      col_names.push_back(*i);
+    return col_names;
+  }
+
+	auto create_XML(std::vector<std::string>& tags, std::vector<std::string> rows)
+	{
+		static int ctr;
+		ptree XMLobjectL;
+		std::string tag, value;
+
+		for (auto i : boost::combine(tags, rows))
+		{
+			//tag contains tags, value contains corresponding values
+			boost::tie(tag, value) = i;
+			XMLobjectL.put("annotation.object." + tag, value);
+		}
+
+		write_xml(std::to_string(ctr) + ".xml", XMLobjectL, std::locale(),
+			xml_writer_make_settings<ptree::key_type>(' ', 1u));
+		ctr++;
+	}
+
+	auto create_JSON(std::vector<std::string>& tags, std::vector<std::string> rows)
+	{
+		static int ctr;
+		ptree XMLobjectL;
+		std::string tag, value;
+
+		for (auto i : boost::combine(tags, rows))
+		{
+			//tag contains tags, value contains corresponding values
+			boost::tie(tag, value) = i;
+			XMLobjectL.put("annotation.object." + tag, value);
+		}
+
+		write_json(std::to_string(ctr) + ".json", XMLobjectL);
+		ctr++;
+	}
+
+	void convertHelper(std::string path, std::string to)
+	{
+		//static int ctr;
+		static std::unordered_map<std::string, int> fileNames;
+		std::vector<std::string> tags;
+		std::vector<std::string> rows;
+		std::ifstream file(path);
+		std::string line;
+		std::vector<std::string> col_names;
+
+		std::getline(file, line);
+		tags = tokenize(line);
+
+		if (to == "xml")
+		{
+			while (std::getline(file, line))
+			{
+				create_XML(tags, tokenize(line));
+			}
+		}
+		else if (to == "json")
+		{
+			while (std::getline(file, line))
+			{
+				create_JSON(tags, tokenize(line));
+			}
+		}
+	}
+
+public:
+	void convert(std::string path, std::string to)
+	{
+		convertHelper(path, to);
+	}
+};
+
+// How to invoke
+/*
+int main() {
+	Convert foo;
+	foo.convert("path_to_csv.csv", "xml");
+	foo.convert("path_to_csv.csv", "json");
+}*/