Merge pull request #491 from morrme/igsieve

sieve: add hint to @Ignore annotations

exercises/sieve/src/test/java/SieveTest.java

         assertEquals(expectedOutput, sieve.getPrimes());
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void findPrimesUpTo10() {
         Sieve sieve = new Sieve(10);
         assertEquals(expectedOutput, sieve.getPrimes());
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void findPrimesUpTo1000() {
         Sieve sieve = new Sieve(1000);