implement SaveAsync() and updated documentation (#42)

* implement SaveAsync() and updated documentation

* fixed re-use of :Save() code, now calls :Save()

DataStore2/init.lua

@@ -12,6 +12,7 @@
 	- BeforeInitialGet(modifier)
 	- BeforeSave(modifier)
 	- Save()
+	- SaveAsync()
 	- OnUpdate(callback)
 	- BindToClose(callback)
 
@@ -405,6 +406,15 @@ function DataStore:Save()
 	end
 end
 
+--[[**
+	<description>
+	Asynchronously saves the data to the data store.
+	</description>
+**--]]
+function DataStore:SaveAsync()
+	coroutine.wrap(DataStore.Save)(self)
+end
+
 --[[**
 	<description>
 	Add a function to be called before the game closes. Fired with the player and value of the data store.