add new DL courses #46

fix stale links; add new DL, ML courses

update ML, BDL courses

update summer school, computer vision and DL sections

update DNN, ML, Optim, RL, PGM, & CV sections

update med. img & bootcamp section

update around the web sec.

minor fix of URL ref

update DL, RL, ML, CV courses

fix stale URLs; update courses in ML, bootcamps

new link to deep learning course (#34)

update courses in CV section

update RL courses

update DL bootcamps section

update courses addressing issues #31 & #32