Add Table Output

Add support for a table output.  This will take any AWS response and generate a pretty printed table.  This can be enabled with `--output table`

This PR adds a dependency on blessings, which is used to add color output and to check the terminal width.  If the terminal width is not large enough to accomodate the default table layout, a vertical table layout is generated instead.  By default, color output is on only if we're writing to a tty but this can be explicitly controlled with the `--color [on|off|auto]` option.