README: Download only takes a while with Git LFS

Author: markus-wa

README.md

@@ -17,7 +17,7 @@ There are also [some other rooms](https://gitter.im/csgodemos) available around
 
 ## Go Get
 
-This might take a while as it downloads the test-data set (~ 10 demos).
+This might take a while if you have Git LFS installed as it downloads the test-data set (~ 10 demos).
 
 	go get -u github.com/markus-wa/demoinfocs-golang