add logger class (#29)

* add logger class

* add LOCATION macro for logger

* added printing in files

examples/logger_example.cpp

@@ -0,0 +1,36 @@
+#include "aare/utils/logger.hpp"
+#include <iostream>
+#include <fstream>
+
+int main() {
+    aare::logger::debug(LOCATION, "hello", 1, "world", std::vector<long>{1, 2, 3, 4, 5});
+    aare::logger::debug(LOCATION, "setting verbosity to INFO");
+    aare::logger::set_verbosity(aare::logger::INFO);
+    aare::logger::debug(LOCATION, "NOTHING SHOULD BE PRINTED");
+    aare::logger::info(LOCATION, "info printed");
+
+
+    // writing to file
+    std::ofstream textfile;
+    textfile.open("Test.txt");
+    aare::logger::set_streams(textfile.rdbuf());
+    aare::logger::info(LOCATION, "info printed to file");
+
+
+
+    // writing with a local logger instance
+    aare::logger::Logger logger;
+    logger.set_verbosity(aare::logger::WARNING);
+    logger.debug(LOCATION, "NOTHING SHOULD BE PRINTED");
+    logger.info(LOCATION, "NOTHING SHOULD BE PRINTED");
+    logger.warn(LOCATION, "warning printed in std::cout");
+    aare::logger::info(LOCATION, "info printed in file ##");
+    textfile.close();
+
+
+    // setting file output by path
+    // user doesn't have to close file
+    aare::logger::set_output_file("Test2.txt");
+    aare::logger::info(LOCATION, "info printed to Test2.txt");
+    return 0;
+}