Handle spaces in directory containing script.
Use delims= to get entire line as arg.
Use dir /b for marks files; fix jump
Prevent extra backslash in paths.
Remove trailing space in mark file.
Jump must first change to the drive.
Add error handling; use .mark for better errors.
Prevent odd mark names.
Change arrow to match original.
Merge pull request #2 from jeremymurray/master

Handle spaces in script path, allow marks on multiple drives, add error handling.