Embedded screenshots in docs are very large #225

Was just looking at the docs and the screenshots now take up considerable more space than I remember.

For example: https://pysurfer.github.io/auto_examples/plot_fmri_activation.html

Here's how it looks to me with my Chrome set to 100% zoom:

Doesn't seem limited to that example.

Did this change when the docs moved to sphinx-gallery? Can the size of the embedded image be controlled (as I assume it used to be?) Having the figures spill over into the sidebar looks messy.