Update Image resizeMode=repeat docs (#106)

* Update Image resizeMode=repeat docs for Android

To go along with facebook/react-native#17404

* Describe actual Image resizeMode=repeat behaviour

* Clarify Image resizeMode=repeat wording

docs/image.md

@@ -254,7 +254,7 @@ Determines how to resize the image when the frame doesn't match the raw image di
 
 * `stretch`: Scale width and height independently, This may change the aspect ratio of the src.
 
-* `repeat`: Repeat the image to cover the frame of the view. The image will keep it's size and aspect ratio. (iOS only)
+* `repeat`: Repeat the image to cover the frame of the view. The image will keep its size and aspect ratio, unless it is larger than the view, in which case it will be scaled down uniformly so that it is contained in the view.
 
 * `center`: Center the image in the view along both dimensions. If the image is larger than the view, scale it down uniformly so that it is contained in the view.