Clarify resampling on beta images vs ROIs

[emdupre]

I'm having a little bit of trouble tracking down the point at which the fLoc defined ROIs

Shape (208, 300, 320)

diverge from the trial-averaged beta images

Shape (76, 90, 71)

Is this noted somewhere in the documentation ?

[emdupre]

I assume it's that the fLoc are acquired at a higher resolution and / or that the target resolution during fMRIPrep is 2mm^3, but given #46 I'm having trouble confirming this