Make sure run_depends get added to pkg manifest as well. Fix #30.

Short-circuit evaluation of the statement determining the value of
'modified_pkg' caused the second call to update_deps(.., 'run_depend', ..)
to never happen. Using binary or to work around that.
Merge pull request #31 from gavanderhoorn/issue30_missing_run_depends

Fix for missing run_depends in generated pkg manifest