acronym: add hint to @Ignore annotations

exercises/acronym/src/test/java/AcronymTest.java

         assertEquals(expected, new Acronym(phrase).get());
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void fromOtherTitleCasedPhrases() {
         final String phrase = "Ruby on Rails";
         assertEquals(expected, new Acronym(phrase).get());
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void fromInconsistentlyCasedPhrases() {
         final String phrase = "HyperText Markup Language";
         assertEquals(expected, new Acronym(phrase).get());
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void fromPhrasesWithPunctuation() {
         final String phrase = "First In, First Out";
         assertEquals(expected, new Acronym(phrase).get());
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void fromOtherPhrasesWithPunctuation() {
         final String phrase = "PHP: Hypertext Preprocessor";
         assertEquals(expected, new Acronym(phrase).get());
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void fromPhrasesWithNonAcronymAllCapsWord() {
         final String phrase = "GNU Image Manipulation Program";
         assertEquals(expected, new Acronym(phrase).get());
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void fromPhrasesWithPunctuationAndSentenceCasing() {
         final String phrase = "Complementary metal-oxide semiconductor";
         assertEquals(expected, new Acronym(phrase).get());
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void fromPhraseWithSingleLetterWord() {
         final String phrase = "Cat in a Hat";