Adding HINTS.md to palindrome-products exercise (#278)

* Cleanup .travis.yml #232

* Added HINTS.md file for nth prime exercise.  Issue #209

* Added HINTS.md for word-search exercise #209

* Revert "Added HINTS.md for word-search exercise #209"

This reverts commit d8ce9a4.

* Revert "Added HINTS.md file for nth prime exercise.  Issue #209"

This reverts commit a2e484c.

* Adding HINTS.md file for palindrome-products exercise

* update to HINTS.md

exercises/palindrome-products/HINTS.md

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+## Hints
+
+For this exercise, you will need to create a set of factors using tuples.
+For more information on tuples, see [this link](https://msdn.microsoft.com/en-us/library/system.tuple(v=vs.110).aspx).