Add more boards

[yuvadm]

Support for other Tiva models is available as well (including with addon shields), but for simplicity's sake they are not included in the repository. They can be added upon request.

[yuvadm]

More board models were added in c3e4c9a

Addon shields are still lacking.

[amalinda]

what is the difference between TivaWare and your repo?

[yuvadm]

Not much except that you can clone this repo immediately while downloading TivaWare is a NightMare™.

[amalinda]

Why is that?

[yuvadm]

Totally unaccessible, hard to find, and hidden behind a registration wall.

[amalinda]

always accessible through http://www.ti.com/tool/sw-tm4c . This code may be outdated but TivaWare is always latest there. Yes, to get their software you need to have a free account.

[yuvadm]

@amalinda If you'd like to add a note that clarifies this in the README I'd be happy to merge a matching PR.