optimize sticky engine

.babelrc

@@ -5,6 +5,8 @@
     "es2015"
   ],
   "plugins": [
-    "transform-class-properties"
-  ]
+      "transform-class-properties",
+      "transform-class-constructor-call",
+      "add-module-exports"
+    ]
 }

README.md

@@ -24,17 +24,31 @@ your css should contain the following lines:
 (you can specify the classNames in js)
 ```css
 .sticky {
+  position: -webkit-sticky;
   position: sticky;
 }
 
 .sticky.sticky-fixed.is-sticky {
+  margin-top: 0;
+  margin-bottom: 0;
   position: fixed;
-  backface-visibility: hidden;
+  -webkit-backface-visibility: hidden;
+          -moz-backface-visibility: hidden;
+       backface-visibility: hidden;
 }
 
-.sticky.sticky-fixed.is-absolute {
+.sticky.sticky-fixed.is-sticky:not([style*="margin-top"]) {
+  margin-top: 0 !important;
+}
+.sticky.sticky-fixed.is-sticky:not([style*="margin-bottom"]) {
+  margin-bottom: 0 !important;
+}
+
+
+.sticky.sticky-fixed.is-absolute{
   position: absolute;
 }
+
 ```
 
 ### js
@@ -63,7 +77,8 @@ static propTypes = {
     absoluteClass:  React.PropTypes.string,
     disabled: React.PropTypes.bool,
     debug: React.PropTypes.bool,
-    tagName: React.PropTypes.string
+    tagName: React.PropTypes.string,
+    scrollClass: PropTypes.object
   };
 
   static defaultProps = {
@@ -75,6 +90,13 @@ static propTypes = {
     absoluteClass: 'is-absolute',
     debug: false,
     disabled: false,
-    tagName: 'div'
+    tagName: 'div',
+    scrollClass: {
+      down: null,
+      up: null,
+      none: null,
+      persist: false,
+      active: false
+    }
   };
 ```