Fixed order of arguments to assert.Len in test files. (#93)

* Fixed order of arguments to assert.Len in test files.

* Added BaseValue funtionality to bar chart

util/math_test.go

@@ -101,7 +101,7 @@ func TestNormalize(t *testing.T) {
 
 	values := []float64{10, 9, 8, 7, 6}
 	normalized := Math.Normalize(values...)
-	assert.Len(5, normalized)
+	assert.Len(normalized, 5)
 	assert.Equal(0.25, normalized[0])
 	assert.Equal(0.1499, normalized[4])
 }