title: unique key prop error in bootstrap-react-table2
body: <p>I have react-bootstrap-table2 and my expandRow function is generating <p> tags with attributes. When I expand data, I can see error</p>
  
  <pre><code>Warning: Each child in a list should have a unique "key" prop.
  Check the render method of `Context.Consumer`.
      in span (at table_chart.js:796)
      in Unknown (created by Body)
      in tbody (created by Body)
      in Body (created by BootstrapTable)
      in table (created by BootstrapTable)
      in div (created by BootstrapTable)
      in BootstrapTable (created by Context.Consumer)
      in RowExpandProvider (created by Context.Consumer)
      in PaginationDataProvider (created by Context.Consumer)
      in SortProvider (created by Context.Consumer)
      in DataProvider (created by BootstrapTableContainer)
      in BootstrapTableContainer (at table_chart.js:828)
      in div (at table_chart.js:826)
      in listChart (at CallsList.js:70)
      in div (at CallsList.js:69)
      in div (at CallsList.js:68)
      in CallsList (at Home.js:36)
      in div (at Home.js:32)
      in Home (at App.js:175)
      in Route (at App.js:175)
      in Switch (at App.js:174)
      in div (at App.js:173)
      in div (at App.js:162)
      in div (at App.js:161)
      in div (at App.js:192)
      in Router (created by BrowserRouter)
      in BrowserRouter (at App.js:191)
      in App (at src/index.js:15)
      in Router (created by BrowserRouter)
      in BrowserRouter (at src/index.js:14)
  </code></pre>
  
  <p>So even each paragraph in expand row need key property? Why? Inside py paragraph are also span, img tags...</p>
  
  <pre><code> renderer: row =&gt; (  
              &lt;div className="tab"&gt;
              {Object.keys(row._source.attrs).sort().map(cell =&gt; 
  
    &lt;p value={row._source.attrs[cell]}&gt; 
                        &lt;span className="spanTab"&gt;{cell}:&lt;/span&gt;
                               &lt;span className="spanTabSmall" &gt;      &lt;img 
   onClick={this.addColumn} field={cell} value={row._source.attrs[cell]}  
    className="icon" alt="addColumnIcon" title="insert column" src= 
  {addColumnIcon} /&gt;   &lt;/span&gt; 
                       &lt;span className="red"&gt;{row._source.attrs[cell]} 
  &lt;/span&gt;
   &lt;/p&gt;
  </code></pre>
  
  <p>The problem is, I can see attributes in generated html table</p>
  
  <pre><code>&lt;p class="tabletd" field="attrs.call-id" value="5147447D-5D137270000333DC- 
  ADC22700"&gt;&lt;span class="spanTab"&gt;call-id: &lt;/span&gt;&lt;span 
   class="spanTabSmall"&gt;      &lt;img field="call-id" title="insert column" 
   value="5147447D-5D137270000333DC-ADC22700" class="icon" 
   alt="addColumnIcon" &gt;&lt;img field="call-id" value="5147447D- 
  5D137270000333DC-ADC22700" title="filter" class="icon" alt="filterIcon"&gt; 
  &lt;img field="call-id" value="5147447D-5D137270000333DC-ADC22700" 
   class="icon" alt="unfilterIcon" title="unfilter" &gt;&lt;/span&gt;&lt;span 
   class="spanTab"&gt;5147447D-5D137270000333DC-ADC22700&lt;/span&gt;&lt;/p&gt;
  </code></pre>
  
  <p>But only name of attribute "call-id" not the value even though it is in tag.</p>