updated the calcDifficulty test to make it clear with what we're testing

test/test.util.js

@@ -189,13 +189,13 @@ describe('util', function() {
   });
   describe('#calcDifficulty', function() {
     var bitsgenesis = 486604799;
-    it('should work for ' + bitsgenesis, function() {
+    it('should work for the bits from the genesis block; ' + bitsgenesis, function() {
       var difficulty = coinUtil.calcDifficulty(bitsgenesis);
       difficulty.should.equal(1);
     });
-    var bitslater = 419476394;
-    it('should work for ' + bitslater, function() {
-      var difficulty = coinUtil.calcDifficulty(bitslater);
+    var randomotherbits = 419476394;
+    it('should work for the bits in a randomly chosen block, eg [00000000000000001fef2bbc6da9b65e16f9187b7d88f15a308490bf2c9b8e1d] ' + randomotherbits, function() {
+      var difficulty = coinUtil.calcDifficulty(randomotherbits);
       difficulty.should.equal(6119726089);
     });
   });