Add 'show byline' option for Facia cards

@stephanfowler & I:

The tool now has a 'showByline' option and an editable byline. Contributor names will automatically be replaced with links, still.

The same tonal colour as the kicker is used for the byline.

In the tool:

![screen shot 2014-09-30 at 12 19 50](https://cloud.githubusercontent.com/assets/1001642/4457193/04d17e2a-4894-11e4-81bd-5cc4aad951d4.png)

On the front:

![screen shot 2014-09-30 at 12 20 03](https://cloud.githubusercontent.com/assets/1001642/4457196/0c7896c2-4894-11e4-95ab-8a7d3133badf.png)

CC @kungpochicken @sndrs @sammorrisdesign @phamann @gklopper