Released netscript version 1.6.7.

added -O, to select an alternative shell to execute for third party programs. added -o, to omit socket reading of supplied character(s). added -m, to change the current working directory of netscript. added -M, to change the root directory of netscript. added $', to change the current working directory via the ruleset. changed standard reading of input to check for the tty name, instead of the generic /dev/tty. changed all related third party executions to use $SHELL. changed some display/text visualizations. fixed segmentation fault introduced in the previous version, when using -u with a user name that doesn't exist. (not a security issue). changed a couple ruleset examples to comply to the new changes.