fix: z-index issues (vuematerial#1264)

* feat(MdCard): remove z-index to prevent card overlap FAB

* fix(MdSelect): fix select content under dialog

* refactor(MdSelect): change order of scss

* docs: remove z-index from main-nav (vuematerial#1134)

* Revert "feat(MdCard): remove z-index to prevent card overlap FAB"

This reverts commit 9e12806.

* feat(MdButton): add fab z-index to prevent overlap

Author: Samuell1

docs/app/template/MainNav.vue

@@ -72,7 +72,6 @@
     top: 64px;
     bottom: 0;
     left: 0;
-    z-index: 2;
     transition: .3s $md-transition-default-timing;
     transition-property: top;
 

src/components/MdButton/MdButton.vue

@@ -220,6 +220,7 @@
   .md-icon-button,
   .md-fab {
     border-radius: 50%;
+    z-index: 10;
 
     &:before {
       border-radius: 50%;

src/components/MdField/MdSelect/MdSelect.vue

@@ -311,20 +311,22 @@
       border: 0;
     }
   }
+  .md-menu-content {
+    z-index: 111;
+    &.md-select-menu {
+      width: 100%;
 
-  .md-menu-content.md-select-menu {
-    width: 100%;
-
-    &.md-menu-content-enter {
-      transform: translate3d(0, -8px, 0) scaleY(.3);
-    }
+      &.md-menu-content-enter {
+        transform: translate3d(0, -8px, 0) scaleY(.3);
+      }
 
-    .md-list {
-      transition: opacity .3s $md-transition-drop-timing;
-    }
+      .md-list {
+        transition: opacity .3s $md-transition-drop-timing;
+      }
 
-    .md-dense .md-ripple.md-list-item-content {
-      font-size: 14px;
+      .md-dense .md-ripple.md-list-item-content {
+        font-size: 14px;
+      }
     }
   }
 </style>