Fix an infinite loop on connection error (this fixes issue #3)

Sometimes, an error happens on the socket, but the 'close' event is called
with "had_errors" set to False.  In this case, we would could ourselves
recursively *twice*, which leads to an exponential number of recursive
calls over time.

This happens, for instance, when DNS resolution fails.

According to the doc, we only need to handle the 'close' event:

  http://nodejs.org/api/net.html#net_event_error_1
Merge pull request #4 from zorun/bugfix

Fix an infinite loop on connection error (closes #3)
Update homepages, emails and authors
Provide a default port (33123) for connecting to Babel

This allows omitting the port number when running babelweb, like:

  babelweb routers="[::1]"
Apply less zoom by default

Actually, the current default zoom level is fine for the linear scale.
But since the logarithmic scale is enabled by default, the default zoom
level should be adapted to the logarithmic scale.

A proper fix would be to have a comparable size for both types of scale,
but that may prove difficult to implement.
Display originated prefixes when hovering a router in the graph

Each Babel router announces a set of prefixes (through "redistribute"
statements), which we call originated prefixes.  This patch displays these
prefixes, as seen by the currently selected router.

Note that for each different selected router, we might see different sets
of originated prefixes, because of prefix filtering performed by various
Babel routers.