add breaking changes to changelog

Author: christopherthielen

CHANGELOG.md

@@ -33,6 +33,7 @@
 
 * **$state:**
   * allow parameters to pass unharmed ([8939d057](https://github.com/angular-ui/ui-router/commit/8939d0572ab1316e458ef016317ecff53131a822))
+    * **BREAKING CHANGE**: state parameters are no longer automatically coerced to strings, and unspecified parameter values are now set to undefined rather than null.
   * allow prevent syncUrl on failure ([753060b9](https://github.com/angular-ui/ui-router/commit/753060b910d5d2da600a6fa0757976e401c33172))
 * **typescript:** Add typescript definitions for component builds ([521ceb3f](https://github.com/angular-ui/ui-router/commit/521ceb3fd7850646422f411921e21ce5e7d82e0f))
 * **uiSref:** extend syntax for ui-sref ([71cad3d6](https://github.com/angular-ui/ui-router/commit/71cad3d636508b5a9fe004775ad1f1adc0c80c3e))
@@ -55,7 +56,7 @@
   * validates whole interface ([32b27db1](https://github.com/angular-ui/ui-router/commit/32b27db173722e9194ef1d5c0ea7d93f25a98d11))
   * implement non-strict matching ([a3e21366](https://github.com/angular-ui/ui-router/commit/a3e21366bee0475c9795a1ec76f70eec41c5b4e3))
   * add per-param config support ([07b3029f](https://github.com/angular-ui/ui-router/commit/07b3029f4d409cf955780113df92e36401b47580))
-
+    * **BREAKING CHANGE**: the `params` option in state configurations must now be an object keyed by parameter name.
 
 ### 0.2.10 (2014-03-12)