Added !default to all variables

First of all, thank you for making this plugin! 
I wanted to overwrite the setting for transitions, but they where missing !default.

scss/_InputRangeVariables.scss

@@ -1,16 +1,16 @@
-$InputRange-fontFamily: 'Helvetica Neue', san-serif;
-$InputRange-primaryColor: #3f51b5;
-$InputRange-neutralColor: #aaaaaa;
-$InputRange-neutralLightColor: #eeeeee;
-$InputRange-disabledColor: #cccccc;
+$InputRange-fontFamily: 'Helvetica Neue', san-serif !default;
+$InputRange-primaryColor: #3f51b5 !default;
+$InputRange-neutralColor: #aaaaaa !default;
+$InputRange-neutralLightColor: #eeeeee !default;
+$InputRange-disabledColor: #cccccc !default;
 
 // InputRange-slider
 $InputRange-slider-background: $InputRange-primaryColor !default;
 $InputRange-slider-border: 1px solid $InputRange-primaryColor !default;
 $InputRange-slider-height: 1rem !default;
 $InputRange-slider-width: 1rem !default;
-$InputRange-slider-transition: transform 0.3s ease-out, box-shadow 0.3s ease-out;
-$InputRange-sliderContainer-transition: left 0.3s ease-out;
+$InputRange-slider-transition: transform 0.3s ease-out, box-shadow 0.3s ease-out !default;
+$InputRange-sliderContainer-transition: left 0.3s ease-out !default;
 $InputRange-slider--active-transform: scale(1.3) !default;
 $InputRange-slider--is-disabled-background: $InputRange-disabledColor !default;
 $InputRange-slider--is-disabled-border: 1px solid $InputRange-disabledColor !default;
@@ -21,6 +21,6 @@ $InputRange-label-color: $InputRange-neutralColor !default;
 // InputRange-track
 $InputRange-track-background: $InputRange-neutralLightColor !default;
 $InputRange-track-height: 0.3rem !default;
-$inputRange-track-transition: left 0.3s ease-out, width 0.3s ease-out;
+$inputRange-track-transition: left 0.3s ease-out, width 0.3s ease-out !default;
 $InputRange-track--active-background: $InputRange-primaryColor !default;
 $InputRange-track--is-disabled-background: $InputRange-neutralLightColor !default;