Documentation problem on cellranger.rst: rsync downloads don't work.

[alanhoyle]

docs/cellranger.rst reads in part:

The example below use the pbmc3k cellranger output files from the 10x website.
First, download the files with the command::
rsync -Lavzp genome-test.gi.ucsc.edu::cells/datasets/pbmc3kCellranger/ ./pbmc3kCellranger/ --progress

When I try running the rsync on our linux cluster, it just hangs indefinitely and times out:

$ rsync -Lavzp genome-test.gi.ucsc.edu::cells/datasets/pbmc3kCellranger/ ./pbmc3kCellranger/ --progress
rsync: [Receiver] failed to connect to genome-test.gi.ucsc.edu (128.114.198.32): Connection timed out (110)
rsync: [Receiver] failed to connect to genome-test.gi.ucsc.edu (2607:f5f0:136:1::26): Network is unreachable (101)
rsync error: error in socket IO (code 10) at clientserver.c(138) [Receiver=3.2.3]

When I try running it on my mac workstation, I get a different error:

> rsync -Lavzp genome-test.gi.ucsc.edu::cells/datasets/pbmc3kCellranger/ ./pbmc3kCellranger/ --progress
@ERROR: Unknown module 'cells'
rsync error: error starting client-server protocol (code 5) at /AppleInternal/Library/BuildRoots/4ff29661-3588-11ef-9513-e2437461156c/Library/Caches/com.apple.xbs/Sources/rsync/rsync/main.c(1402) [receiver=2.6.9]

I suspect this same issue would also affect the instructions in docs/scanpy.rst and docs/seurat.rst