Fix class in loader.py

[cool-RR]

The dynamically defined class in loader.py causes bugs on Python 3 when using multiple sub-loaders, since there are multiple InnerLoader classes defined in the same scope and the latter overrides the formers' names, which causes an exception when calling super.

I suggest fixing it by having a separate function that'll dynamically define the class. (Or the best way would be to find a way to get rid of the dynamically defined class.)

[jiaaro]

Yeah, I think the current approach is suffering a bit from my getting too clever. Would like to simplify it when I have some free time (which of course never seems to happen)

[cool-RR]

FYI: Currently you can't use multiple sub-loaders to the Shpaml loader in Python 3.

[l0kix2]

It seems that multiple subloaders feature doesn't work in python 2.x also.