Write log output to a file instead of just stderr

* Log output to a file (currently update-log.txt in the updater's current directory)
 * Use correct stream type for Log::m_output

src/Log.cpp

@@ -80,3 +80,9 @@ void Log::write(Type type, const char* text)
 	}
 }
 
+std::string Log::defaultPath()
+{
+	std::string path = "update-log.txt";
+	return path;
+}
+

src/Log.h

@@ -22,11 +22,12 @@ class Log
 		void write(Type type, const char* text);
 
 		static Log* instance();
+		static std::string defaultPath();
 	
 	private:
 		static void writeToStream(std::ostream& stream, Type type, const char* text);
 
-		std::fstream m_output;
+		std::ofstream m_output;
 };
 
 inline void Log::write(Type type, const std::string& text)

src/main.cpp

@@ -29,6 +29,7 @@ void runUpdaterThread(void* arg)
 
 int main(int argc, char** argv)
 {
+	Log::instance()->open(Log::defaultPath());
 	UpdaterOptions options;
 	options.parse(argc,argv);