///
/// Generates `placeholder` content for a given element.
///
/// @author romamatusevich
///
/// @link http://caniuse.com/#feat=css-placeholder caniuse
/// @link http://www.w3.org/html/wg/drafts/html/master/single-page.html#the-placeholder-attribute spec
/// @link https://developer.mozilla.org/en-US/docs/Web/CSS/:-moz-placeholder MDN
/// @link http://css-tricks.com/snippets/css/style-placeholder-text css-tricks
///
/// @output
/// ```css
///    &::-webkit-input-placeholder {
///        <content>
///    }
///    &::-moz-placeholder {
///        <content>
///    }
///    &:-ms-input-placeholder {
///        <content>
///    }
/// ```
///
/// @example
///   .selector {
///     @include x-placeholder {
///         color: #bada55;
///         font-weight: bold;
///     }
///   }
///
@mixin x-placeholder {
	&::-webkit-input-placeholder {
		@content // Chrome, Safari, Opera
	}
	&::-moz-placeholder {
		@content // Firefox 19+
	}
	&:-ms-input-placeholder {
		@content // IE 10+
	}
}