Replace react-addons-shallow-compare (#123)

`react-addons-shallow-compare` is deprecated.

Keep the original `shouldComponentUpdate` for checking  `shouldFreeze` flag

should address #87

package.json

@@ -1,6 +1,6 @@
 {
   "name": "react-stickynode",
-  "version": "2.1.0",
+  "version": "2.1.1",
   "description": "A performant and comprehensive React sticky",
   "main": "index.js",
   "scripts": {
@@ -32,7 +32,7 @@
   "dependencies": {
     "classnames": "^2.0.0",
     "prop-types": "^15.6.0",
-    "react-addons-shallow-compare": "^0.14.2 || ^15.0.0",
+    "shallowequal": "^1.0.0",
     "subscribe-ui-event": "^2.0.0"
   },
   "devDependencies": {

src/Sticky.jsx

@@ -11,7 +11,7 @@ import PropTypes from 'prop-types'
 
 import {subscribe} from 'subscribe-ui-event';
 import classNames from 'classnames';
-import shallowCompare from 'react-addons-shallow-compare';
+import shallowEqual from 'shallowequal';
 
 // constants
 const STATUS_ORIGINAL = 0; // The default status, locating at the original position.
@@ -356,7 +356,7 @@ class Sticky extends Component {
     }
 
     shouldComponentUpdate (nextProps, nextState) {
-        return !this.props.shouldFreeze() && shallowCompare(this, nextProps, nextState);
+        return !this.props.shouldFreeze() && !(shallowEqual(this.props, nextProps) && shallowEqual(this.state, nextState));
     }
 
     render () {