retain relevant interface bindings when splitting edges
new function for testing if overlay present in anm
string repr of anm
access corresponding interface across overlays (if exists)
correct returning edges to use new interface binding format of {node_id: interface_id}
testing code for interfaces
testing code for interfaces
updating interface support
more work on interfaces
fix issue with ibgp levels
Merge pull request #110 from sk2/master

merge updates back to vrf branch
fix bug where passing in empty list would fall back to all nodes in graph

now check if nbunch is None rather than evaluating to False (which was
case for empty list)
only look at neighbouring routers for vrf (handles switches, other devices)
look at neighbouring routers
fix support for wrapping exploded edges
add todo
concat rather than nested lists
handle connected components
switch support for isis, ospf, ebgp
fix multipoint ebgp session handling to obtain ips