added _.uniqueId definition

lodash/lodash-tests.ts

@@ -771,6 +771,8 @@ result = <any[]>_.times(3, function(n: number) { this.cast(n); }, mage);
 
 result = <string>_.unescape('Moe, Larry &amp; Curly');
 
+result = <string>_.uniqueId('contact_');
+result = <string>_.uniqueId();
 
 //////////////////////////////////////////////////////////////////////////////////////////////////
 

lodash/lodash.d.ts

@@ -2844,24 +2844,14 @@ declare module _ {
 	* @return The unescaped string.
 	**/
 	export function unescape(
-		string: string): string;
-
-	
-
-	
+		string: string): string;	
 
 	/**
-	* Generate a globally-unique id for client-side models or DOM elements that need one.
-	* If prefix is passed, the id will be appended to it. Without prefix, returns an integer.
-	* @param prefix A prefix string to start the unique ID with.
-	* @return Unique string ID beginning with `prefix`.
+	* Generates a unique ID. If prefix is provided the ID will be appended to it.
+	* @param prefix The value to prefix the ID with.
+	* @return Returns the unique ID.
 	**/
-	export function uniqueId(prefix: string): string;
-
-	/**
-	* @see _.uniqueId
-	**/
-	export function uniqueId(): number;
+	export function uniqueId(prefix?: string): string;