README.md: how to download a single example (flutter#615)

Author: noamraph

README.md

@@ -10,6 +10,21 @@ A collection of open source samples that illustrate best practices for
 The easiest way to browse through the samples in this repo (as well as a few others!)
 is the [visual samples index](https://flutter.github.io/samples).
 
+## Tip: minimize download size
+
+As this repository is quite big, you can use svn to download a single example.
+For example:
+
+```
+svn co https://github.com/flutter/samples/trunk/provider_shopper
+```
+
+You can also use a shallow clone to download just the latest revision:
+
+```
+git clone --depth 1 https://github.com/flutter/samples.git
+```
+
 ## Interested in contributing?
 
 See the [contributor's guide](CONTRIBUTING.md)!