fix(toolbar): remove transition duration for $ngAnimate

* Other components, like `md-toolbar` use a custom transition on the background-color, color etc, but the related CSS selector has a high specificity.

* So for example, when ng-hide is applied, then we set the transition to `none`.
But that's not working sometimes, because the both selectors have the same specificity.

To fix this, we can apply `!important` or increase the selector specificity by using a CSS hack.

https://www.w3.org/TR/CSS2/cascade.html#specificity

The toolbar selector has in our case a specificity of 20.
* .md-button.ng-hide // 0,0,2,0
* .md-toolbar-tools .md-button // 0,0,2,0

------
So this is actually a thing, which is caused by $ngAnimate, which is not
able to solve this issue.

We need to reset the transition duration, when $ngAnimate looks for it,
manually.

$ngAnimate Issue: angular/angular.js#8224 (comment)

Fixes #7929

Closes #8190

src/components/button/button.scss

@@ -71,6 +71,9 @@ button.md-button::-moz-focus-inner {
     text-decoration: none;
   }
 
+  // By default $ngAnimate looks for transition durations on the element, when using ng-hide, ng-if, ng-show.
+  // The .md-button has a transition duration applied, which means, that $ngAnimate delays the hide process.
+  // To avoid this, we need to reset the transition, when $ngAnimate looks for the duration.
   &.ng-hide, &.ng-leave {
     transition: none;
   }

src/components/toolbar/toolbar.scss

@@ -30,7 +30,8 @@ md-toolbar {
   min-height: $baseline-grid * 8;
   width: 100%;
 
-  transition: $swift-ease-in-out;
+  transition-duration: $swift-ease-in-out-duration;
+  transition-timing-function: $swift-ease-in-out-timing-function;
   transition-property: background-color, fill, color;
 
   &.md-whiteframe-z1-add, &.md-whiteframe-z1-remove {
@@ -47,6 +48,13 @@ md-toolbar {
     box-sizing: border-box;
   }
 
+  // By default $ngAnimate looks for transition durations on the element, when using ng-hide, ng-if, ng-show.
+  // The toolbar has a transition duration applied, which means, that $ngAnimate delays the hide process.
+  // To avoid this, we need to reset the transition, when $ngAnimate looks for the duration.
+  &.ng-animate {
+    transition: none;
+  }
+
   &.md-tall {
     height: $toolbar-tall-height;
     min-height: $toolbar-tall-height;
@@ -116,8 +124,16 @@ md-toolbar {
     margin-bottom: 0;
 
     &, &.md-icon-button md-icon {
-      transition: $swift-ease-in-out;
+      transition-duration: $swift-ease-in-out-duration;
+      transition-timing-function: $swift-ease-in-out-timing-function;
       transition-property: background-color, fill, color;
+
+      // Normally .md-button is already resetting the transition, when $ngAnimate looks for the duration,
+      // but in this case, the selector has a higher specificity than the `reset selector`, which means, that
+      // we need to reset the transition our self.
+      &.ng-animate {
+        transition: none;
+      }
     }
   }
   &> .md-button:first-child {