bump version to v0.13.0 and fill in the changelog and the upgrade docs

docs/changelog.rst

@@ -6,6 +6,11 @@ Development
 ===========
 - (Fill this out as you fix issues and develop your features).
 
+Changes in 0.13.0
+=================
+- POTENTIAL BREAKING CHANGE: Added Unicode support to the `EmailField`, see
+  docs/upgrade.rst for details.
+
 Changes in 0.12.0
 =================
 - POTENTIAL BREAKING CHANGE: Fixed limit/skip/hint/batch_size chaining #1476

docs/upgrade.rst

@@ -6,6 +6,17 @@ Development
 ***********
 (Fill this out whenever you introduce breaking changes to MongoEngine)
 
+0.13.0
+******
+This release adds Unicode support to the `EmailField` and changes its
+structure significantly. Previously, email addresses containing Unicode
+characters didn't work at all. Starting with v0.13.0, domains with Unicode
+characters are supported out of the box, meaning some emails that previously
+didn't pass validation now do. Make sure the rest of your application can
+accept such email addresses. Additionally, if you subclassed the `EmailField`
+in your application and overrode `EmailField.EMAIL_REGEX`, you will have to
+adjust your code to override `EmailField.USER_REGEX`, `EmailField.DOMAIN_REGEX`,
+and potentially `EmailField.UTF8_USER_REGEX`.
 
 0.12.0
 ******

mongoengine/__init__.py

@@ -23,7 +23,7 @@ __all__ = (list(document.__all__) + list(fields.__all__) +
            list(signals.__all__) + list(errors.__all__))
 
 
-VERSION = (0, 12, 0)
+VERSION = (0, 13, 0)
 
 
 def get_version():