Remove third_party/polymer from .gitignore

third_party/polymer/v1_0/components/paper-button/README.md

-paper-button
-============
-
-Material Design: <a href="http://www.google.com/design/spec/components/buttons.html">Buttons</a>
-
-`paper-button` is a button. When the user touches the button, a ripple effect emanates
-from the point of contact. It may be flat or raised. A raised button is styled with a
-shadow.
-
-Example:
-```html
-    <paper-button>flat button</paper-button>
-    <paper-button raised>raised button</paper-button>
-    <paper-button noink>No ripple effect</paper-button>
-```
-You may use custom DOM in the button body to create a variety of buttons. For example, to
-create a button with an icon and some text:
-
-```html
-    <paper-button>
-      <iron-icon icon="favorite"></iron-icon>
-      custom button content
-    </paper-button>
-```
-## Styling
-
-Style the button with CSS as you would a normal DOM element.
-
-```css
-    /* make #my-button green with yellow text */
-    #my-button {
-        background: green;
-        color: yellow;
-    }
-```
-By default, the ripple is the same color as the foreground at 25% opacity. You may
-customize the color using this selector:
-
-```css
-    /* make #my-button use a blue ripple instead of foreground color */
-    #my-button::shadow paper-ripple {
-      color: blue;
-    }
-```
-The opacity of the ripple is not customizable via CSS.