Refactored rspec-focus.txt to rspec-focus.sh.
Fixed dotfile symlinking for nested folder structures.

- If the nested folder structure doesn't exist, then it is created.
Updated Silver Surfer error message for RSpec Focus pre-commit hook.
Refactored Silver Surfer command check for RSpec focus pre-commit
hook.

- The Silver Surfer exit code is suppressed (i.e. || true) so the
  script doesn't prematurely exit.
- Due to suppression of the exit code, we can get an empty string
  array when The Silver Surfer finds nothing. The if statement was
  updated to ignore arrays of this type.