Behind a firewall (or issues with network connectivity) can't build a social network from pubmed file

[risserlin]

If there are issues with your internet or if you are behind a firewall you can not build a scoial network even if you are using a pubmed xml file.

In this case, shouldn't crash with error message. Needs a warning that unable to connect to Pubmed in order to get supplementary info. Build network anyways minus the missing citation information.