Update changelog and prepare for 0.9 (#3025)

This commit updates the CHANGELOG and prepares for the 0.9 release. This
should be the last commit on master prior to the 0.9 release.

CHANGELOG.md

@@ -15,6 +15,8 @@ The format is based on [Keep a Changelog].
 
 ## [UNRELEASED]
 
+## [0.9.0] - 2019-08-22
+
 ### Deprecated
 
 -   The gates `U` and `CX` are being deprecated in favor of `u3` and
@@ -97,8 +99,10 @@ The format is based on [Keep a Changelog].
 -   Replaces `LegacySwap` by faster, more stable `StochasticSwap` pass (\#2672)
 -   Uses level 1 by default as transpiler optimization level (\#2672)
 -   Change `Snapshot` signature to match `simulator.snapshot` (\#2592)
--   `DAGCircuit.width()` formerly returned number of qubits, now returns total number of qubits + classical bits (\#2564)
--   Functions assuming the former semantics of `DAGCircuit.width()` now call `DAGCircuit.num_qubits()` (\#2564)
+-   `DAGCircuit.width()` formerly returned number of qubits, now returns total
+    number of qubits + classical bits (\#2564)
+-   Functions assuming the former semantics of `DAGCircuit.width()` now call
+    `DAGCircuit.num_qubits()` (\#2564)
 -   `DAGCircuit.num_cbits()` renamed to `DAGCircuit.num_clbits()` (\#2564)
 -   Changed definition of `Cu3Gate` to to equivalent to the canonical
     definition of a controlled `U3Gate` (\#2755)
@@ -1254,7 +1258,8 @@ The format is based on [Keep a Changelog].
 -   Correct operator precedence when parsing expressions (\#190).
 -   Fix \"math domain error\" in mapping (\#111, \#151).
 
-[UNRELEASED]: https://github.com/Qiskit/qiskit-terra/compare/0.8.2...HEAD
+[UNRELEASED]: https://github.com/Qiskit/qiskit-terra/compare/0.9.0...HEAD
+[0.9.0]: https://github.com/Qiskit/qiskit-terra/compare/0.8.2...0.9.0
 [0.8.2]: https://github.com/Qiskit/qiskit-terra/compare/0.8.1...0.8.2
 [0.8.1]: https://github.com/Qiskit/qiskit-terra/compare/0.8.0...0.8.1
 [0.8.0]: https://github.com/Qiskit/qiskit-terra/compare/0.7.2...0.8.0

releasenotes/notes/0.9/dag-draw-method-968b6fa96050e255.yaml

@@ -0,0 +1,9 @@
+---
+features:
+  - |
+    A ``DAGCircuit`` object (i.e. the graph representation of a QuantumCircuit where
+    operation dependencies are explicit) can now be visualized with the ``.draw()``
+    method. This is in line with Qiskit's philosophy of easy visualization.
+    Other objects which support a ``.draw()`` method are ``QuantumCircuit``,
+    ``PassManager``, and ``Schedule``.
+