Expand tabs
Modify usage message in advance
Implement -s option
Make chols search keywords only in basename of cho directory
Implement -k option
Separate show_dirline from main
Obsolete chogrep
Add help to options
Remove unimplemented help
Merge pull request #6 from kazutomi/merge_chols_chogrep

chogrep is replaced with chols -k; for compatibility, chogrep is left to invoke chols -k with warning message.

Now chols has the following options:

* -l: Long format (shows touched date)
* -k: Also search in title file [new]
* -s: Case-strict search [new]
* -h: Show help