add+doc percent() to Rotary

README.md

@@ -88,6 +88,12 @@ Examples:
 * `set(min_val=0, max_val=59)` change encoder bounds - useful to set minutes on a clock display
 * `set(value=6)`  change encoder value to `6`.  calling `value()` will now return `6`
 ***
+`percent(scale=100.0)` Return the encoder value in percent
+
+Examples:
+* `percent()` Return the encoder value in percent (0.0 through 100.0)
+* `percent(scale=1.0)` Return the encoder value in the range 0.0 through 1.0
+***
 `reset()` set encoder value to `min_val`.  Redundant with the addition of the `set()` method.  Retained for backwards compatibility)
 ***
 `add_listener(function)` add a callback function that will be called on each change of encoder count

rotary.py

@@ -112,6 +112,9 @@ def set(self, value=None, min_val=None, incr=None,
     def value(self):
         return self._value
 
+    def percent(self, scale=100.0):
+        return scale * (self._value - self._min_val) / (self._max_val - self._min_val)
+
     def reset(self):
         self._value = 0