Add support to the float slider

IPython/html/static/widgets/js/widget_float.js

@@ -9,6 +9,10 b' define(['
     var IntTextView = int_widgets.IntTextView;
 
     var FloatSliderView = IntSliderView.extend({
+        _validate_text_input: function(x) {
+            return parseFloat(x);
+        },
+
         _validate_slide_value: function(x) {
             // Validate the value of the slider before sending it to the back-end
             // and applying it to the other views on the page.