Request images from API directly instead of thru waiter redirect

[clekstro]

We discussed this a long, long time ago in https://github.com/travis-pro/team-teal/issues/1077. I've tested the markdown links, but would feel more comfortable testing the other image types a bit more before merging.

[igorwwwwwwwwwwwwwwwwwwww]

I think there is some branding value in keeping it under the main domain. the same way you can git clone [email protected]/<repo>, you can use travis-ci.org/<repo>.svg for status badges.

getting rid of that redirect is a super good idea though. an alternative approach we could consider is installing the nginx buildpack on web and proxying the badges instead of redirecting.