Doesn't incorporate the options from the shell variant, which for now
lives in commandlog-log.sh.

...turns out this isn't installed by default, which probably should have
been obvious.

Make command log accept -o option

Make command log accept -[NUM] argument

The -o option is used to specify columns to display in output, for
instance if you want to show only the date and command rather than all
columns in the commands table.

It seem intuitive to pass an argument of the format -[NUM] (where [NUM]
is a number) to any command where you tail logs.

This commit adds the -[NUM] functionality to commandlog-log function as
well as handles help output.

Fixes #2

Generalize user home dir

Use the `$HOME` env var rather than hard-code.

This change should be POSIX compliant and work across shells.