Update README.md

Author: cheton

README.md

@@ -205,6 +205,38 @@ import { Button } from './components/Buttons';
 </Button>
 ```
 
+## API
+
+### Properties
+
+#### Button
+
+Name | Type | Default | Description 
+:--- | :--- | :------ | :----------
+componentClass | Function or String | 'button' |
+type | One of:<br/>'button'<br/>'reset'<br/>'submit' | 'button' |
+btnSize | One of:<br/>'lg'<br/>'md'<br/>'sm'<br/>'xs'<br/>'large'<br/>'medium'<br/>'small'<br/>'extra-small' | 'md' |
+btnStyle | One of:<br/>'default'<br/>'primary'<br/>'danger'<br/>'emphasis'<br/>'border'<br/>'flat'<br/>'link'<br/> | 'default' |
+active | Boolean | false |
+hover | Boolean | false |
+focus | Boolean | flase |
+disabled | Boolean | flase |
+block | Boolean | false |
+compact | Boolean | false |
+
+#### ButtonGroup
+
+Name | Type | Default | Description 
+:--- | :--- | :------ | :----------
+btnSize | One of:<br/>'lg'<br/>'md'<br/>'sm'<br/>'xs'<br/>'large'<br/>'medium'<br/>'small'<br/>'extra-small' | |
+btnStyle | One of:<br/>'default'<br/>'primary'<br/>'danger'<br/>'emphasis'<br/>'border'<br/>'flat'<br/>'link'<br/> | |
+vertical | Boolean | false |
+
+#### ButtonToolbar
+
+Name | Type | Default | Description 
+:--- | :--- | :------ | :----------
+
 ## License
 
 MIT