Support for Adafruit Pixie (#749)

* Support for Adafruit Pixie

* Updated based on PR review to align with library style and added Pixie constructor to NeoPixelBugLg

src/NeoPixelBus.h

@@ -84,6 +84,13 @@ public:
     {
     }
 
+    NeoPixelBus(uint16_t countPixels, Stream* pixieStream) :
+        _countPixels(countPixels),
+        _state(0),
+        _method(countPixels, T_COLOR_FEATURE::PixelSize, T_COLOR_FEATURE::SettingsSize, pixieStream)
+    {
+    }
+
     ~NeoPixelBus()
     {
     }