Fixes scikit-learn#7329 and scikit-learn#6483

I realize this is deprecated, but in case you're still interested in a quick bugfix, my understanding is that this was previously a silent bug even in Python 2.7.

```
import numpy as np

def check_mse(n_eval, batch_size):

    y, MSE = np.zeros(n_eval), np.zeros(n_eval)
    for k in range(max(1, n_eval / batch_size)):
        batch_from = k * batch_size
        batch_to = min([(k + 1) * batch_size + 1, n_eval + 1])
    
        print batch_from, batch_to

def check_mse_fixed(n_eval, batch_size):

    y, MSE = np.zeros(n_eval), np.zeros(n_eval)
    for k in range(int(n_eval / float(batch_size) + 0.5)):
        batch_from = k * batch_size
        batch_to = min([(k + 1) * batch_size + 1, n_eval + 1])
    
        print batch_from, batch_to
        
        
check_mse(8, 3)
print
check_mse_fixed(8, 3)
```
Python 2.7 output:
```
0 4
3 7

0 4
3 7
6 9
```
Note 8 corresponds to the sample size so the current version (if converted to an int) would miss the last few samples.

* fix batch

* add test for eval_MSE

…ikit-learn#7330)

* fix batch

* add test for eval_MSE

…ikit-learn#7330)

* fix batch

* add test for eval_MSE

…ikit-learn#7330)

* fix batch

* add test for eval_MSE