Add analysis scripts for averaging and plotting contours

[BrendaQiu]

Adding contour.py to hcpannot/analysis and average_contour.ipynb to work directory.

[BrendaQiu]

Also adding lmm.py and lmm.ipynb that analyze and visualize LMM results

[noahbenson]

Sorry to submit this a little late; overall the code is good, just needs to be updated in places to use the proc system instead of the cache files, plus some minor tweaks.

[noahbenson]

I think this can just be defaultdict(dict) since you don't actually use contour_data[hemi][tag].append(...) anywhere.