test showing a bug in accord-net/framework/#13 along with the fix

in [NaiveBayes`1.cs:293](https://github.com/accord-net/framework/blob/ffe224211f01784b8a2354ac0b6aa19dbb0e98d3/Sources/Accord.MachineLearning/Bayes/NaiveBayes%601.cs#L293) we see the following
``` csharp
public NaiveBayes(int classes, int inputs, TDistribution[,] priors, double[] classPriors)
{
    if (classes <= 0) throw new ArgumentOutOfRangeException("classes");
    if (priors == null) throw new ArgumentNullException("priors");
    if (priors.Length != classes) throw new DimensionMismatchException("priors");
    if (classPriors.Length != classes) throw new DimensionMismatchException("classPriors");
```

The condition in the second line from bottom is incorrect for multidimensional arrays, whose `.Length` property returns the total number of elements in the array.  What we want here instead is `.GetLength(0)` to get the size of the first dimension.