[doc] Add changelog for 0.54.1 release

CHANGELOG.md

+## v0.54.1 (9th May 2019)
+- `Transaction`: add __eq__() and __hash__() methods
+- Transaction Unlock parameters: add __eq__() and __hash__() methods
+- Transaction: add 'time' variable for read and write but not for doc generation
+- output conditions: add __eq__() and __hash__() methods
+- test transaction equality at all levels
+
+---
+
+- Thanks @Moul, @vtexier
+
 ## v0.54.0 (5th May 2019)
 
 ### Code/tests
@@ -16,6 +27,8 @@
 - setup.py: add classifiers: Python versions, Intended Audience
 - Add CHANGELOG.md from v0.53.1
 
+---
+
 - Thanks @Moul, @vtexier
 
 ## v0.53.1 (18 April 2019)