Initial read-daemon for hwmon entries

Discoveres hwmon entries for fans, input voltage, and temperature
sensors.  Polls entries on a 1s interval and displays a message to
stdout if one of the entries have changed.
diff --git a/hwmon.H b/hwmon.H
new file mode 100644
index 0000000..494d38e
--- /dev/null
+++ b/hwmon.H
@@ -0,0 +1,23 @@
+#ifndef __HWMON_H
+#define __HWMON_H
+
+#include <string>
+
+namespace hwmon
+{
+    using namespace std::literals;
+
+    namespace entry
+    {
+        static const std::string input = "input"s;
+    }
+
+    namespace type
+    {
+        static const std::string fan = "fan"s;
+        static const std::string temp = "temp"s;
+        static const std::string volt = "in"s;
+    }
+}
+
+#endif