Implemented get_view_before_times()

docs/HTML/DataFrame.html

@@ -362,6 +362,10 @@ <H2 ID="2"><font color="blue">API Reference with code samples <font size="+4">&#
       <td title="Gets data or view at specified time"><a href="https://htmlpreview.github.io/?https://github.com/hosseinmoein/DataFrame/blob/master/docs/HTML/get_data_at_times.html">get_data_at_times()<BR>get_view_at_times()</a></td>
     </tr>
 
+    <tr class="item" onmouseover="this.style.backgroundColor='#ffff66';" onmouseout="this.style.backgroundColor='#d4e3e5';">
+      <td title="Gets data or view before specified time"><a href="https://htmlpreview.github.io/?https://github.com/hosseinmoein/DataFrame/blob/master/docs/HTML/get_data_before_times.html">get_data_before_times()<BR>get_view_before_times()</a></td>
+    </tr>
+
     <tr class="item" onmouseover="this.style.backgroundColor='#ffff66';" onmouseout="this.style.backgroundColor='#d4e3e5';">
       <td title="Gets data or view by index"><a href="https://htmlpreview.github.io/?https://github.com/hosseinmoein/DataFrame/blob/master/docs/HTML/get_data_by_idx.html">get_data_by_idx( 2 )<BR>get_view_by_idx( 2 )</a></td>
     </tr>

docs/HTML/get_data_at_times.html

@@ -53,9 +53,9 @@
       </td>
       <td>
         This selects the rows using the index column at specified time. It returns another DataFrame with selected data indexed by DateTime. Self is unchanged.<BR><BR>
-        <B>NOTE</B>: The index column type must be DateTime or it won’t compile<BR>
+        <B>NOTE</B>: The index column type must be DateTime or it won't compile<BR>
       </td>
-      <td>
+      <td width="33%">
         <B>Ts</B>: List all the types of all data columns. A type should be specified in the list only once.<BR>
         <B>hour</B>: Specified hour<BR>
         <B>minute</B>: Specified minute<BR>
@@ -79,7 +79,7 @@
         It behaves like get_data_at_times(), but it returns a View. A view is a DataFrame that is a reference to the original DataFrame. So if you modify anything in the view the original DataFrame will also be modified.<BR><BR>
         <B>NOTE</B>: There are certain operations that you cannot do with a view. For example, you cannot add/delete columns, etc.<BR>
       </td>
-      <td>
+      <td width="33%">
         <B>Ts</B>: List all the types of all data columns. A type should be specified in the list only once.<BR>
         <B>hour</B>: Specified hour<BR>
         <B>minute</B>: Specified minute<BR>
@@ -102,7 +102,7 @@
       <td>
           Same as above view, but it returns a <I>const</I> view. You can not change data in const views. But if the data is changed in the original DataFrame or through another view, it is reflected in the const view.       
       </td>
-      <td>
+      <td width="33%">
         <B>Ts</B>: List all the types of all data columns. A type should be specified in the list only once.<BR>
         <B>hour</B>: Specified hour<BR>
         <B>minute</B>: Specified minute<BR>