Support for all user on unix env

[yimiaoxiehou]

In unix sys, vfox will create .version-fox dir on cur home. it just use for cur user. if want to use in diff user, will download multi times.

I try move /root/.version-fox to /.version-fox and create soft link to /root/.version-fox and /home/yimiao/.version-fox, it also only work for root ,no with yimiao.

/.version-fox dir have 755 permission

[aooohan]

Similar to #45