update changelog: rycrx varform
@@ -23,6 +23,7 @@ Added
- Relative-Phase Toffoli gates `rccx` (with 2 controls) and `rcccx`
(with 3 controls).
+- Variational form `RYCRX`
[0.5.1](https://github.com/Qiskit/qiskit-aqua/compare/0.5.0...0.5.1) - 2019-05-24
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