update CHANGELOG for 0.5.0

CHANGELOG.rst

 Change Log
 ==========
 
-0.5.0: XXXX/YY/ZZ
+0.5.0: 2021/04/20
 -----------------
 
 * esrf
-    * TomoScanBase: add properties `sequence_name`, `sample_name` and `group_size`
+    * TomoScanBase
+        * add `sequence_name`, `sample_name` and `group_size` properties
+        * add `start_time` and `end_time` properties
+        * add `x_translation`, `y_translation` and `z_translation` properties (Not handled by EDFTomoScan for now)
+        * HDF5TomoScan
+            * speed up sinogram generation
+        EDFTomoscan
+            * improve lazy loading
     * utils: add the concept of groups. A group for example is a set of sequences defining a zseries
 
 0.4.0: 2020/11/09