Added new "worldborder.bypass" permission which will allow a person to move around outside the border without being knocked back. This permission is not granted to anyone by default, even Ops, and is not included in the "worldborder.*" permission set.

Thanks to st-remy and guyag for pull requests close to what I ended up implementing here.
Merge branch 'master' of github.com:Brettflan/WorldBorder
Added artificial height limit for Nether worlds, to work around CraftBukkit bug which reports a max height of 255 for them, leading to players being teleported on top of the "roof" of the Nether at height 127
Added a couple of new safe blocks to the list
Allow knockback to be set to 0, for the rare person that might for whatever reason want to disable border knockback
Fix for command to enable/disable Dynmap border display not reporting correctly whether it's now enabled or disabled when run

Also added variables for Dynmap border color/thickness/opacity, just for internal clarity... will also simplify things if I or someone else ever gets around to adding settings for those values, to allow them to be changed
Release version 1.5.5
Polish up border bypass handling a bit
0 knockback was glitchy; fixed

Also attempt to fix problem when riding mobs via MobRider where mob and player end up underground after knockback; seems unsuccessful. Seeing as pigs in vanilla CraftBukkit without MobRider don't have this problem, but _do_ have the problem along with all other mobs when MobRider is loaded, I'm not bothering with this one further for now.
Real Release 1.5.5
Reworked border bypass to be toggleable by command, instead of always on if player had the permission like it was.

New command /wb bypass [player] [on/off], which allows the player to go beyond the border without being knocked back. Requires "worldborder.bypass" permission (Ops only by default). Nobody has bypass mode enabled by default (has to be toggled on), and the list of people with bypass enabled is wiped on server restarts. Player name ("[player]") is optional if run in-game and defaults to the player running the command, but must be specified if run from console. If on or off ("[on/off]") is not specified, it will simply be toggled.
Release version 1.6.0

Also added bypass to worldborder.* permission set since it now only enables the command rather than permanently forcing bypass mode.
Update readme and logo PSD
Whenever a chunk is loaded on the server, a check will now be run to make sure the border-monitoring task is still running like it should be. It will be restarted if necessary.
Release 1.6.1