Use a warning for the deprecation notice

stevenharman · stevenharman · commit 62571447e55b · 2020-10-17T15:45:21.000-04:00
diff --git a/lib/git_tracker/runner.rb b/lib/git_tracker/runner.rb
@@ -19,7 +19,8 @@ def self.init
     end
 
     def self.install
-      puts "`git-tracker install` is deprecated. Please use `git-tracker init`"
+      warn("`git-tracker install` is deprecated. Please use `git-tracker init`", uplevel: 1)
+
       init
     end
 
