args: new line-numbering option, and fixes

* Introduced a new -n/--number option to print line number
* Fix terminal width detection (subtract width of '...')
* Quote $args so that more than one white spaces printed as-is
* If colums > 60, show tail 10 chars as well for long argus
[args] NEW: --color and --escape options.
Merge branch 'master' of github.com:ryo1kato/fewliners