message: Wrote docs for Box-Cox visitor
diff: @@ -333,7 +333,7 @@ table.hovertable td {
  <tr onmouseover="this.style.backgroundColor='#ffff66';" onmouseout="this.style.backgroundColor='#d4e3e5';">
  <td title="Loads index and multiple columns at the same time"><a href="https://htmlpreview.github.io/?https://github.com/hosseinmoein/DataFrame/blob/master/docs/HTML/load_data.html">load_data</a>( )</td>
  - <td></td>
  + <td title="Specification for Box-Cox transformation">enum class <a href="https://htmlpreview.github.io/?https://github.com/hosseinmoein/DataFrame/blob/master/docs/HTML/BoxCoxVisitor.html">box_cox_type</a>{ }</td>
  <td title="Calculates standard error of the mean">struct <a href="https://htmlpreview.github.io/?https://github.com/hosseinmoein/DataFrame/blob/master/docs/HTML/SEMVisitor.html">SEMVisitor</a>{ }</td>
  <td></td>
  </tr>
  @@ -453,7 +453,7 @@ table.hovertable td {
  <tr onmouseover="this.style.backgroundColor='#ffff66';" onmouseout="this.style.backgroundColor='#d4e3e5';">
  <td title="Bucketizes column data in self"><a href="https://htmlpreview.github.io/?https://github.com/hosseinmoein/DataFrame/blob/master/docs/HTML/bucketize.html">self_bucketize</a>( )</td>
  <td></td>
  - <td></td>
  + <td title="Calculates Box-Cox transformation">struct <a href="https://htmlpreview.github.io/?https://github.com/hosseinmoein/DataFrame/blob/master/docs/HTML/BoxCoxVisitor.html">BoxCoxVisitor</a>{ }</td>
  <td></td>
  </tr>
  