Add basic query for HP 3457A

src/labtoolkit/DigitalMultimeter/HP3457A.py

@@ -1,4 +1,14 @@
 from ..IEEE488 import IEEE488
 
+
 class HP3457A(IEEE488):
-    ...
+
+    def __post__(self):
+        self.inst.write_termination = '\n'
+        self.inst.read_termination = '\r\n'
+        # self.write('OFORMAT ASCII')
+
+    @property
+    def reading(self):
+        return self.query_float('?')
+