fix(slide-toggle): remove host element margin (#3761)

* Angular Material components should not have any outer-margin on component host elements. Similar as for the checkbox component.

Author: devversion

src/demo-app/slide-toggle/slide-toggle-demo.scss

@@ -2,4 +2,8 @@
   display: flex;
   flex-direction: column;
   align-items: flex-start;
-}
+
+  md-slide-toggle {
+    margin: 6px 0;
+  }
+}

src/lib/slide-toggle/slide-toggle.scss

@@ -7,7 +7,6 @@
 $mat-slide-toggle-thumb-size: 20px !default;
 $mat-slide-toggle-bar-border-radius: 8px !default;
 $mat-slide-toggle-height: 24px !default;
-$mat-slide-toggle-margin: 16px !default;
 $mat-slide-toggle-spacing: 8px !default;
 $mat-slide-toggle-ripple-radius: 23px !default;
 $mat-slide-toggle-bar-width: 36px !default;
@@ -19,7 +18,6 @@ $mat-slide-toggle-bar-track-width: $mat-slide-toggle-bar-width - $mat-slide-togg
   display: inline-block;
   height: $mat-slide-toggle-height;
 
-  margin: $mat-slide-toggle-margin 0;
   line-height: $mat-slide-toggle-height;
 
   white-space: nowrap;