fix format

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
add intra-node messages in readme

Link: https://github.com/GeneAssembly/biosal/issues/115
Link: https://github.com/GeneAssembly/biosal/issues/114
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
use message constructor

Link: https://github.com/GeneAssembly/biosal/issues/112
Link: https://github.com/GeneAssembly/biosal/issues/111
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
don't use message_set_tag

Link: https://github.com/GeneAssembly/biosal/issues/110
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>