the code for merging things on the left works

Link: https://github.com/sebhtml/ray/issues/188
Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>
complete the implementation of the seed merger

However, edges for remote seeds are not correct because a given
seed can not have 2 seeds on its right listed in the gossip
package.

Link: https://github.com/sebhtml/ray/issues/188
Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>