[enh] update CHANGELOG.md

CHANGELOG.md

+## v0.50.5 (21/03/2020)
+### Bugs
+* Fix send money to pubkey with search user selected
+
+### Tests
+* Update and fix pytest suite
+* Update duniter-mirage dependency version
+
+### Enhancements
+* Tx history update button set to disable until update is done
+* Increase delay between network crawlings to 1 mn
+
+### CI/CD
+* Add format and tests stage in .gitlab-ci.yml
+
 ## v0.50.4 (18/03/2020)
 ### Code
-* fix session closed error (regression in v0.50.3)
+* Fix session closed error (regression in v0.50.3)
 
 ## v0.50.3 (16/03/2020)
 ### Code
-* fix exception when refresh tx history
-* fix Unclosed client session error (at last !)
+* Fix exception when refresh tx history
+* Fix Unclosed client session error (at last !)
 ### CI/CD
-* fix bug with setuptools 28.8.x version in gitlab CI/CD image
+* Fix bug with setuptools 28.8.x version in gitlab CI/CD image
 
 ## v0.50.2 (10/03/2020)
 ### Code