Issues in IO Image Notebooks

Some issues in io image notebooks:
1. In record_io.ipynb cell No.9:
```python
s = mx.recordio.pack_img(header, data, quality=100, img_fmt='.jpg')
```
results in segmentation fault.

2. In advanced_img_io.ipynb cell No.9:
```python
img = cv2.imread('test_images/ILSVRC2012_val_00000001.JPEG', flags=1)
```
results in segmentation fault. I searched this online and found it might be an opencv bug.

3. In image_io.ipynb cell No.5:
MXNetError: [07:28:27] src/io/input_split_base.cc:163: Check failed: files_.size() != 0U (0 vs. 0) Cannot find any files that matches the URI patternz ./data/caltech_train.rec

All these tests were run on AMI Ubuntu. I also rebuilt mxnet using updated github version.
@piiswrong Any idea?