Save NodeInfo instead of repeatedly re-constructing it

Hello @kylehardgrave, 

Please review the following commits I made in branch 'nick-prefixes'.

a37b08597d3af660915855ce053ef26141b74ee9 (2013-07-10 13:28:55 -0400)
Validate node names

3cf51ff83b80764f292f7561f7b2273801434a94 (2013-07-10 13:08:02 -0400)
Store the builds() nodes as Nodes instead of as strings


R=@kylehardgrave