Update Issue #306: cytidine to cytosine

exercises/nucleotide-count/src/test/java/NucleotideTest.java

 
     @Ignore
     @Test
-    public void testRepetitiveCytidineGetsCounted() {
+    public void testRepetitiveCytosineGetsCounted() {
         DNA dna = new DNA("CCCCC");
         assertThat(dna.count('C'), is(5));
     }