Switched to cStringIO (oops)
Now properly parses only days with events.
Proper workaround for no event dates
dynamic_countries is no longer present by default
No longer throws an error on empty history entries

For some reason, in 1.8.1 there are now empty history entries in save
files, eg:

1448.1.1 =
{
}

This commit fixes an exception thrown when such entries were
encountered.