Tutorial Updates

[iancze]

AK Sco data has old flagging format (i.e., the flags must be flipped in order to not exclude all of the data)?

To get the tutorial to work, need to do the following: in "src/visibilities.jl", I changed "ch_flag = flag[:,i]" to something like "ch_flag = .!flag[:,i]".

[report contributed by J. Pegues.]