fix(button): alignment between anchor buttons and normal buttons

* Currently a normal button is not properly aligning with an anchor button (only when using a flexbox layout parent)
  The buttons should align properly without using flexbox, since those are actually inline-blocks.
  See: http://codepen.io/DevVersion/pen/GqBrYb

* This accounts also for icon buttons. Having a normal icon button and an anchor button makes the icon alignment incorrect and inconsistent.
  See: http://codepen.io/DevVersion/pen/dXjVgQ?editors=1010

Fixes #2440.

Closes #9183

src/components/button/button.scss

@@ -26,29 +26,36 @@ button.md-button::-moz-focus-inner {
 }
 
 .md-button {
+  display: inline-block;
+  position: relative; // Required for absolute canvas child elements.
+  cursor: pointer;
+
+  /** Alignment adjustments */
+  min-height: $button-line-height;
+  min-width: $button-min-width;
+  line-height: $button-line-height;
+
+  vertical-align: middle;
+  align-items: center;
+  text-align: center;
+
   border-radius: $button-border-radius;
   box-sizing: border-box;
-  color: currentColor;
 
+  /* Reset default button appearance */
   user-select: none;
-  position: relative; //for child absolute-positioned <canvas>
-
   outline: none;
   border: 0;
-  display: inline-block;
-  align-items: center;
+
+  /** Custom styling for button */
   padding: $button-padding;
   margin: $button-margin;
-  line-height: $button-line-height;
-  min-height: $button-line-height;
+
   background: transparent;
+  color: currentColor;
   white-space: nowrap;
-  // override for FAB, icon buttons, etc.
-  min-width: $button-min-width;
 
-  text-align: center;
-
-  // Always uppercase buttons
+  /* Uppercase text content */
   text-transform: uppercase;
   font-weight: 500;
   font-size: $body-font-size-base;
@@ -57,8 +64,8 @@ button.md-button::-moz-focus-inner {
   font-family: inherit;
   text-decoration: none;
 
-  cursor: pointer;
-  overflow: hidden;   // for ink containment
+  // Ink Ripple should not create any overflow.
+  overflow: hidden;
 
   transition: box-shadow $swift-ease-out-duration $swift-ease-out-timing-function,
               background-color $swift-ease-out-duration $swift-ease-out-timing-function;