Update publish script to target phoenix_test.ex

Since the setup instructions have moved from the README to
`phoenix_test.ex`, we update the publish script to target
`phoenix_test.ex`.

Author: germsvel

bin/publish

@@ -5,7 +5,7 @@ set -e
 previous_version="${1}"
 release_version="${2}"
 
-sed -i '' "s/$previous_version/$release_version/" README.md
+sed -i '' "s/$previous_version/$release_version/" lib/phoenix_test.ex
 sed -i '' "s/$previous_version/$release_version/" mix.exs
 
 git add .