Reworked logo and colors

[gbevin]

While working on docs and looking at the pretty exception output, I felt that the colors and the logo needed a little refresh. I obviously added '2' but also picked new blue and orange colors that look good both on white and dark backgrounds.

The pretty exception engine colors have been adapted to be the same.

[booniepepper]

I like it!

[joshaustin]

Looking nice!