Add Table Output


![ec2tabledark](https://f.cloud.github.com/assets/368057/228287/8c4c90ec-867b-11e2-90df-12b635923985.jpg)
![ec2tablelight](https://f.cloud.github.com/assets/368057/228291/a0d00094-867b-11e2-897b-46d5a18774bc.jpg)

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.