fix readme

Author: hirosassa

README.md

@@ -9,5 +9,5 @@ Machine learning tasks which are used with data pipeline library "luigi" and its
 
 ## Dependencies
 
-You should install `tensorflow = ">=1.13.1,<2.0"` manually if you would like to use some models under `redshells/contrib` directory.
+You should add `tensorflow = ">=1.13.1,<2.0"` on your app dependencies if you would like to use some models under `redshells/contrib` directory.
 `Tensorflow` is not included redshells' dependencies because there are some models not used it.