fix #77

* Implement basic usage of table <caption> element

Add tableCaption prop, which can be a component / string

Add simple test and an example to Storybook

* Fix Caption example & Code syle fix for return statement

* Rename tableCaption > caption

packages/react-bootstrap-table2-example/examples/basic/table-with-caption.js

@@ -0,0 +1,47 @@
+import React from 'react';
+
+import { BootstrapTableful } from 'react-bootstrap-table2';
+import Code from 'components/common/code-block';
+import { productsGenerator } from 'utils/common';
+
+const products = productsGenerator();
+
+const columns = [{
+  dataField: 'id',
+  text: 'Product ID'
+}, {
+  dataField: 'name',
+  text: 'Product Name'
+}, {
+  dataField: 'price',
+  text: 'Product Price'
+}];
+
+const sourceCode = `\
+const columns = [{
+  dataField: 'id',
+  text: 'Product ID'
+}, {
+  dataField: 'name',
+  text: 'Product Name'
+}, {
+  dataField: 'price',
+  text: 'Product Price'
+}];
+
+const CaptionElement = () => <h3 style={{ borderRadius: '0.25em', textAlign: 'center', color: 'purple', border: '1px solid purple', padding: '0.5em' }}>Component as Header</h3>;
+
+<BootstrapTableful keyField="id" data={ products } caption="Plain text header" columns={ columns } />
+
+<BootstrapTableful keyField="id" data={ products } caption={<CaptionElement />} columns={ columns } />
+`;
+
+const Caption = () => <h3 style={{ borderRadius: '0.25em', textAlign: 'center', color: 'purple', border: '1px solid purple', padding: '0.5em' }}>Component as Header</h3>;
+
+export default () => (
+  <div>
+    <BootstrapTableful keyField="id" data={ products } caption="Plain text header" columns={ columns } />
+    <BootstrapTableful keyField="id" data={ products } caption={<Caption />} columns={ columns } />
+    <Code>{ sourceCode }</Code>
+  </div>
+);