fix(typescript): Fix strictNullCheck type error

Closes #33
Closes angular-ui/ui-router#3499

Author: christopherthielen

src/transition/interface.ts

@@ -758,18 +758,18 @@ export type IStateMatch = Predicate<StateDeclaration>
  * ```
  */
 export interface HookMatchCriteria {
-  [key: string]: HookMatchCriterion;
+  [key: string]: HookMatchCriterion | undefined;
 
   /** A [[HookMatchCriterion]] to match the destination state */
-  to?: HookMatchCriterion | undefined;
+  to?: HookMatchCriterion;
   /** A [[HookMatchCriterion]] to match the original (from) state */
-  from?: HookMatchCriterion | undefined;
+  from?: HookMatchCriterion;
   /** A [[HookMatchCriterion]] to match any state that would be exiting */
-  exiting?: HookMatchCriterion | undefined;
+  exiting?: HookMatchCriterion;
   /** A [[HookMatchCriterion]] to match any state that would be retained */
-  retained?: HookMatchCriterion | undefined;
+  retained?: HookMatchCriterion;
   /** A [[HookMatchCriterion]] to match any state that would be entering */
-  entering?: HookMatchCriterion | undefined;
+  entering?: HookMatchCriterion;
 }
 
 export interface IMatchingNodes {