Incorporate additional open source datasets into the pretraining step

[reesekneeland]

This issue will likely follow from #8

The goals for incorporating more data are:

• Expanding the prior to encompass simple stimuli
• Pretrain on imagery trials from other datasets
• Pretrain on more vision data to see general improvements in the models.

Some candidate datasets are below, these will probably have varying levels of utility for this project.
Generic Object Decoding
Deep Image Reconstruction
NeuroMod
CMI Neuroimaging Dataset