Support `rm -rf`

[Drake-Eidukas]

With git, you can run git rm -rf <dir> to remove a directory, but this fails with cfg.

drake@element:~/workspace/test_base$ cfg rm lol
error: 'git rm --cached lol' failed
error: exit status 128
output: fatal: not removing 'lol' recursively without -r
drake@element:~/workspace/test_base$ cfg rm lol -r
Error: unknown shorthand flag: 'r' in -r
Usage:
  cfg rm [flags]

Flags:
  -h, --help   help for rm

Global Flags:
      --global-config string   global config file (default is $HOME/.cfg.yaml)

unknown shorthand flag: 'r' in -r

[Drake-Eidukas]

Related: There's the todo message--

// TODO: intelligently order filePaths to remove
// all instances of a templ before removing the templ

We should document this intended functionality in the CLI help message, as well as figure out how exactly we want to go about doing this-- should it be that if you rm a template that other templates are based on, you rm those child templates?