[readme] update changelog to indicate breaking changes
Note that `IntoEdges` and `IntoEdgesDirected` were present in 0.4.
diff --git a/README.rst b/README.rst
index 2a63a1c..ffcae0e 100644
--- a/README.rst
+++ b/README.rst
@@ -29,13 +29,26 @@
- 0.5.0
- - Upgrade to Rust 2018 edition
- - Fix clippy warnings and unify code formatting
- - Improved and enhanced documentation
- - Update dependencies including modern quickcheck
- - Numerous bugfixes and refactorings
- - Added ``MatrixGraph`` implementation
- - Added ``InfoEdges`` and ``InfoEdgesDirected``
+ - Breaking changes:
+
+ - The iterative DFS implementation, ``Dfs``, now marks nodes visited when
+ they are pushed onto the stack, not when they're popped off. This may
+ require changes to callers that use ``Dfs::from_parts`` or manipulate
+ its internals.
+ - The ``IntoEdgesDirected`` trait now has a stricter contract for
+ undirected graphs. Custom implementations of this trait may have to be
+ updated. See the `trait documentation`__ for more.
+
+ - Other changes:
+
+ - Upgrade to Rust 2018 edition
+ - Fix clippy warnings and unify code formatting
+ - Improved and enhanced documentation
+ - Update dependencies including modern quickcheck
+ - Numerous bugfixes and refactorings
+ - Added ``MatrixGraph`` implementation
+
+__ https://docs.rs/petgraph/0.5/petgraph/visit/trait.IntoEdgesDirected.html
- 0.4.13
