Update Changelog

CHANGELOG.md

+# 1.2.0
+
+- Improve use experience with SSL certificates
+  + We now load the system CA bundle if it exists (fix errors when running inside G5K)
+- Misc:
+  + Grid5000 shell colors
+  + RST doc regenerated
+
+# 1.1.3
+
+- Fix metrics endpoints
+
 # 1.1.2
 
 - Extract a API method to authenticate from python