Add slider in init

Author: b-yogesh

chartlets.py/chartlets/components/__init__.py

@@ -2,14 +2,15 @@
 from .button import Button
 from .button import IconButton
 from .checkbox import Checkbox
+from .charts.vega import VegaChart
 from .progress import CircularProgress
 from .progress import CircularProgressWithLabel
 from .progress import LinearProgress
 from .progress import LinearProgressWithLabel
-from .charts.vega import VegaChart
 from .radiogroup import Radio
 from .radiogroup import RadioGroup
 from .select import Select
+from .slider import Slider
 from .switch import Switch
 from .tabs import Tab
 from .tabs import Tabs