armstrong-numbers: add reference to tutorial (#1470)

* Add hints.md to armstrong-numbers

* Regenerate armstrong-numbers README

exercises/armstrong-numbers/.meta/hints.md

+For more help on how to solve this exercise, please refer to the tutorial provided as part of the hello world exercise:
+[TUTORIAL.md](https://github.com/exercism/java/blob/master/exercises/hello-world/TUTORIAL.md)

exercises/armstrong-numbers/README.md

 
 Write some code to determine whether a number is an Armstrong number.
 
+# Java Tips
+
+For more help on how to solve this exercise, please refer to the tutorial provided as part of the hello world exercise:
+[TUTORIAL.md](https://github.com/exercism/java/blob/master/exercises/hello-world/TUTORIAL.md)
+
+
 # Running the tests
 
 You can run all the tests for an exercise by entering