[JOSS] ambiguous data path in paper example

[platipodium]

In the JOSS paper, you write

ds_clim = nc.open_data("sst.mon.mean.nc")
ds_present = nc.open_data("data/sst.mon.mean.nc")

This is misleading. Are both datasets the same file? Why in different folders?

See openjournals/joss-reviews#5494

[platipodium]

... and while you're at it, the title command exceeds the line length, so you could introduce a line break :=)

[robertjwilson]

Path is now fixed along with line break.