Minor fixes for encoding and call of undefined methods

[che85]

fixes #32
fixes #30

[SachidanandAlle]

Looks good to me

[wyli]

I was having issues without the encoding... #26

[che85]

@wyli That's odd. I tested without the encoding on MacOS and Redhat Linux and it works for me.

[phcerdan]

Tested locally, and this makes the plugin usable in Linux. Tested with Slicer release 5.6.1.

EDIT: Not really, cannot make it work with just LoadImaged, it crashes with no message.

====================================================================
Run:: monai.transforms.LoadImaged(keys=['image', 'label'], ensure_channel_first=True)
====================================================================
error: [/path/Slicer-5.6.1-linux-amd64/bin/SlicerApp-real] exit abnormally - Report the problem.