pangram: add hint to @Ignore annotations

Ref. #448

exercises/pangram/src/test/java/PangramCheckerTest.java

         assertFalse(pangramChecker.isPangram(""));
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void pangramWithOnlyLowerCaseLettersIsRecognizedAsPangram() {
         assertTrue(pangramChecker.isPangram("the quick brown fox jumps over the lazy dog"));
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void phraseMissingCharacterXIsNotPangram() {
         assertFalse(pangramChecker.isPangram("a quick movement of the enemy will jeopardize five gunboats"));
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void anotherPhraseMissingCharacterXIsNotPangram() {
         assertFalse(pangramChecker.isPangram("the quick brown fish jumps over the lazy dog"));
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void pangramWithUnderscoresIsRecognizedAsPangram() {
         assertTrue(pangramChecker.isPangram("\"the_quick_brown_fox_jumps_over_the_lazy_dog\""));
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void pangramWithNumbersIsRecognizedAsPangram() {
         assertTrue(pangramChecker.isPangram("\"the 1 quick brown fox jumps over the 2 lazy dogs\""));
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void phraseWithMissingLettersReplacedByNumbersIsNotPangram() {
         assertFalse(pangramChecker.isPangram("\"7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog\""));
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void pangramWithMixedCaseAndPunctuationIsRecognizedAsPangram() {
         assertTrue(pangramChecker.isPangram("\"Five quacking Zephyrs jolt my wax bed.\""));
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void pangramWithNonAsciiCharactersIsRecognizedAsPangram() {
         assertTrue(pangramChecker.isPangram("Victor jagt zwölf Boxkämpfer quer über den großen Sylter Deich."));
     }
 
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void panagramInAlphabetOtherThanAsciiIsNotRecognizedAsPangram() {
         assertFalse(pangramChecker.isPangram("Широкая электрификация южных губерний даст мощный толчок подъёму сельского хозяйства."));
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void upperAndLowerCaseVersionsOfTheSameCharacterShouldNotBeCountedSeparately() {
         assertFalse(pangramChecker.isPangram("the quick brown fox jumped over the lazy FOX"));