Add box commands
Revise the main help
Add `pecrant dir` instead of `pecrant list`

refs GH-3

In order to use the pipe, leave "pecrant list" command to output all columns.
Merge pull request #5 from gongo/pecrant-dir

Add `pecrant dir` instead of `pecrant list`
Support directory that contains space
Merge pull request #6 from gongo/contains-space

Support directory that contains space
Merge remote-tracking branch 'yungsang/box'