`tuckr pop` does not support popping individual files/directories

I consider "pop" to be the opposite behaviour of "push", and so I think tuckr pop should do the inverse of tuckr push.

Currently, tuckr pop just removes the group and cleans up its symbolic links (ie tuckr rm some_group && rm Configs/some_group), whereas tuckr push begins with the given files already existing on the system.

As such, I think it would be logical for tuckr pop to restore any symbolic linked files from some_group to just be regular old files, ie: for each file in some_group:

1. Copy the file from the dotfiles repository to its install location on the system, replacing the symbolic link
2. Remove the file from the dotfiles.

This would also lend itself nicely to allowing specific files to be given as arguments to tuckr pop, expanding the usefulness of the command.

Start by tracing the tuckr pop and tuckr push command paths and running both against a sample group with symbolic links. Define how group and individual-file arguments should behave, then verify that popping restores regular files at their install locations and removes the corresponding files from the dotfiles repository.