[Shotwell] Missing dependency in build from source instructions

[Bruno Girin]

Hi all,

I just found out that the instructions to build from source found
here: http://yorba.org/shotwell/install/#source are missing one
dependency on Ubuntu: libjson-glib-dev. So if you're trying to build
from source and get an error message when building the publishing
plugins that it cannot find glib.h, add the missing dependency.

Cheers,

Bruno