[doc] Add CHANGELOG.md from v0.53.1

CHANGELOG.md

+## v0.54.0 (XX April 2019)
+
+### Code/tests
+- Fix OutputSource and InputSource from_inline() regex matching
+- Transaction document: tests and code: drop versions 2 and 3 management
+- Block document: code: drop vensions 2 and 3 management
+- Block document: Upgrade blocks to v11 and TX to v10
+- Add OutputSource.inline_condition() method
+
+### Other
+- CI: Do not trigger build, tests, type check on modification of non-relevant files
+- Makefile: use python3 module to run tests and type check
+- Add coveralls as dev dependency
+- setup.py: add classifiers: Python versions, Intended Audience
+- Add CHANGELOG.md from v0.53.1
+
+- Thanks @Moul, @vtexier
+
+## v0.53.1 (18 April 2019)
+
+- Implement equality `__eq__()` and `__hash__()` methods for InputSource and OutputSource classes
+
+Thanks @Moul, @vtexier
+
+## v0.53.0 (30 March 2019)
+
+- To be completed…