Update Slack plugin compatability
Update Slack plugin compatability

The Slack plugin now supports 0.4.0+ thanks to a pull request from @Flink. This is a small update to the docs to reflect this.
Evlos/dokku,jimjag/dokku,vijayviji/dokku,jimjag/dokku,fmoliveira/dokku,dokku/dokku,alexquick/dokku,expa/dokku,fruitl00p/dokku,alexquick/dokku,sseemayer/dokku,econya/dokku,pmvieira/dokku,fmoliveira/dokku,expa/dokku,elia/dokku,u2mejc/dokku,econya/dokku,claytonbrown/dokku,vijayviji/dokku,elia/dokku,Evlos/dokku,amaltson/dokku,u2mejc/dokku,callahad/dokku,expa/dokku,amaltson/dokku,claytonbrown/dokku,bobvanderlinden/dokku,Evlos/dokku,callahad/dokku,johnfraney/dokku,fmoliveira/dokku,sseemayer/dokku,dokku/dokku,callahad/dokku,Cactusbone/dokku,AnselZhangGit/dokku,pmvieira/dokku,Cactusbone/dokku,johnfraney/dokku,alessio/dokku,alexquick/dokku,pmvieira/dokku,fmoliveira/dokku,progrium/dokku,Cactusbone/dokku,dokku/dokku,AnselZhangGit/dokku,jimjag/dokku,sseemayer/dokku,callahad/dokku,econya/dokku,Evlos/dokku,fruitl00p/dokku,Cactusbone/dokku,vijayviji/dokku,codeconfab/dokku,netbrick/dokku,elia/dokku,claytonbrown/dokku,bobvanderlinden/dokku,johnfraney/dokku,alexquick/dokku,elia/dokku,crisward/dokku,fmoliveira/dokku,AnselZhangGit/dokku,fmoliveira/dokku,johnfraney/dokku,progrium/dokku,Cactusbone/dokku,bobvanderlinden/dokku,progrium/dokku,crisward/dokku,expa/dokku,econya/dokku,elia/dokku,AnselZhangGit/dokku,crisward/dokku,AnselZhangGit/dokku,amaltson/dokku,econya/dokku,jimjag/dokku,bobvanderlinden/dokku,callahad/dokku,vijayviji/dokku,Evlos/dokku,sseemayer/dokku,crisward/dokku,elia/dokku,u2mejc/dokku,codeconfab/dokku,amaltson/dokku,expa/dokku,alexquick/dokku,dokku/dokku,fmoliveira/dokku,johnfraney/dokku,jimjag/dokku,amaltson/dokku,Cactusbone/dokku,expa/dokku,sseemayer/dokku,fmoliveira/dokku,AnselZhangGit/dokku,progrium/dokku,vijayviji/dokku,elia/dokku,progrium/dokku,crisward/dokku,fruitl00p/dokku,alessio/dokku,alexquick/dokku,codeconfab/dokku,fruitl00p/dokku,netbrick/dokku,dokku/dokku,econya/dokku,alessio/dokku,Evlos/dokku,codeconfab/dokku,u2mejc/dokku,vijayviji/dokku,claytonbrown/dokku,progrium/dokku,econya/dokku,Cactusbone/dokku,jimjag/dokku,pmvieira/dokku,callahad/dokku,alessio/dokku,u2mejc/dokku,u2mejc/dokku,codeconfab/dokku,dokku/dokku,netbrick/dokku,alessio/dokku,bobvanderlinden/dokku,crisward/dokku,fruitl00p/dokku,callahad/dokku,u2mejc/dokku,bobvanderlinden/dokku,pmvieira/dokku,johnfraney/dokku,claytonbrown/dokku,sseemayer/dokku,claytonbrown/dokku,netbrick/dokku,dokku/dokku,progrium/dokku,vijayviji/dokku,pmvieira/dokku,u2mejc/dokku,Evlos/dokku,alessio/dokku,pmvieira/dokku,bobvanderlinden/dokku,vijayviji/dokku,jimjag/dokku,claytonbrown/dokku,elia/dokku,AnselZhangGit/dokku,johnfraney/dokku,crisward/dokku,sseemayer/dokku,Cactusbone/dokku,alessio/dokku,netbrick/dokku,claytonbrown/dokku,callahad/dokku,fruitl00p/dokku,bobvanderlinden/dokku,fruitl00p/dokku,econya/dokku,crisward/dokku,pmvieira/dokku,netbrick/dokku,netbrick/dokku,expa/dokku,alessio/dokku,amaltson/dokku,codeconfab/dokku,amaltson/dokku,fruitl00p/dokku,jimjag/dokku,netbrick/dokku,codeconfab/dokku,AnselZhangGit/dokku,Evlos/dokku,progrium/dokku,dokku/dokku,codeconfab/dokku,amaltson/dokku,expa/dokku,sseemayer/dokku,alexquick/dokku,alexquick/dokku,johnfraney/dokku