Updated badges

This is to address:

https://github.com/swcarpentry/site/issues/5

And changes to PNGs will need to by synced there.

- removed unused core badge
- added helper badge SVG and PNG
- updated the following badge SVG with backported PNG colors:
	- instructor
	- creator
	- organizer
- Added learner PNG badge, with colors from old core badge
- Updated learner PNG from green/creator color, to blue scheme

A couple other notes, I edited these in Adobe Illustrator - and to preserved editing, enabled embedding illustrator specific editing data (an option in the SVG save dialog). I also set the updated SVG artboards to be square - facilitating the square export of the PNG.

The PNGs seemed to use a copyrighted typeface, "Museo 700", this is a serif font, but you can't really tell in the small PNGs - I've gone with Ariel Bold, as it is more universal, however opening these in inkscape and the font renders differently. I don't think we have achieved the promise of SVG being a good portable universal format yet.