test directory initialization

add test coverage for getRoot and getInitialCwd

fix asylumfunk#26
refactor CWD

check for strict equality
declare variables in a single statement
call them "directories" not "folders"
return this for chaining
use single quotes

fix asylumfunk#27
Merge pull request #22 from asylumfunk/issue/26

test directory initialization
Merge pull request #23 from asylumfunk/issue/27

refactor CWD