Edit and correct readme for better readability (#4)

* edit readme for better readability and correct english

* add browser compatibility note

* edit readme package weight and wording

README.md

@@ -1,8 +1,10 @@
 # Sal [![npm version](https://badge.fury.io/js/sal.js.svg)](https://www.npmjs.com/package/sal.js) [![License: MIT](https://img.shields.io/badge/License-MIT-blue.svg)](https://github.com/mciastek/sal/blob/master/LICENSE) [![Build Status](https://travis-ci.org/mciastek/sal.svg?branch=master)](https://travis-ci.org/mciastek/sal)
 
-Performance focused, lightweight (less than **2.5 kb**) scroll animation library, written in vanilla JavaScript. No dependencies!
+Performance focused, lightweight (less than **2.8 kb**) scroll animation library, written in vanilla JavaScript. No dependencies!
 
-**Sal** (_Scroll Animation Library_) is written with aim to provide performant and lightweight solution for animating elements on scroll. It's based on the [Intersection Observer](https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API), which gives amazing performance in terms of checking the element's presence in viewport.
+**Sal** (_Scroll Animation Library_) was created to provide a performant and lightweight solution for animating elements on scroll. It's based on the [Intersection Observer](https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API), which gives amazing performance in terms of checking the element's presence in the viewport.
+
+**Note:** Intersection Observer API is an experimental technology so be sure to consult the [browser compatibility table](https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API#Browser_compatibility) and consider using a [polyfill](https://github.com/w3c/IntersectionObserver/tree/master/polyfill).
 
 ## Table of Contents
 - [Install](#install)
@@ -22,7 +24,7 @@ $ npm install --save sal.js
 $ yarn add sal.js
 ```
 
-Then load it with your favorite module loader or use as global, when no modules
+Load it with your favorite module loader or use as a global variable
 
 ```js
 // ES6 modules
@@ -44,36 +46,36 @@ And remember to add styles
 
 ## Usage
 
-In HTML, add `data-sal`, which value is animation name, e.g.:
+In HTML, add a `data-sal` attribute with the animation name as value, e.g.:
 
 ```html
-<div data-sal="<animation-name>"></div>
+<div data-sal="fade"></div>
 ```
 
-Then simply init Sal in your script file:
+Then simply initialize Sal in your script file:
 
 ```js
 sal();
 ```
 
-It will look for an element with `data-sal` attribute and launch animation, when it's in viewport.
+It will look for all elements with a `data-sal` attribute and launch their animation when in viewport.
 
 ## Animations
-With **sal.js** you can easily change animation's options, by adding a proper `data` attribute:
-- `data-sal-duration` - changes animation's duration
-- `data-sal-delay` - adds delay to animation
+In **sal.js** you can easily change animation's options, by adding a proper `data` attribute:
+- `data-sal-duration` - changes duration of the animation
+- `data-sal-delay` - adds delay to the animation
 - `data-sal-easing` - sets easing for the animation
 
 For example:
 ```html
 <div
   data-sal="slide-up"
-  data-sal-delay='300'
-  data-sal-easing='ease-out-bounce'
+  data-sal-delay="300"
+  data-sal-easing="ease-out-bounce"
 ></div>
 ```
 
-Library supports several animations:
+The library supports several animations:
 - `fade`
 - `slide-up`
 - `slide-down`
@@ -90,9 +92,9 @@ Library supports several animations:
 
 | Property | Type | Description | Default  |
 |---------------------------|-------------|---------------|---------|
-| `threshold` | Number | Percentage of element's area that needs to be visible to launch animation (see [docs](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/thresholds)) | 0.5 |
-| `once` | Boolean | Defines if animation needs to be launched once | true |
-| `disable` | Boolean | Flag for disabling animations | false |
+| `threshold` | Number | Percentage of an element's area that needs to be visible to launch animation (see [docs](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/thresholds)) | `0.5` |
+| `once` | Boolean | Defines if animation needs to be launched once | `true` |
+| `disable` | Boolean | Flag for disabling animations | `false` |
 
 You can set options during Sal's initialization, e.g.:
 
@@ -107,10 +109,10 @@ sal({
 
 | Property | Type | Description | Default  |
 |---------------------------|-------------|---------------|---------|
-| `selector` | String | Selector of element, which should be animated | [data-sal] |
-| `animateClassName` | String | Class name which triggers animation | sal-animate |
-| `disabledClassName` | String | Class name which defines disable state | sal-disabled |
-| `rootMargin` | String | Corresponds to root's bounding box margin (see [docs](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/rootMargin)) | 0% 50% |
+| `selector` | String | Selector of the elements to be animated | `[data-sal]` |
+| `animateClassName` | String | Class name which triggers animation | `sal-animate` |
+| `disabledClassName` | String | Class name which defines the disabled state | `sal-disabled` |
+| `rootMargin` | String | Corresponds to root's bounding box margin (see [docs](https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver/rootMargin)) | `0% 50%` |
 
 ## API