Bonus: Travis-CI build-checking

Now Travis-CI will watch for changes in this repo, and re-build it in their virtual environment to make sure we didn’t F anything up.  For free!

• DrawInQuad Xcode scheme now has the Pods scheme as a build prerequisite.
• New `.travis.yml` specifies just the basics: language, xcode_workspace file, and xcode_scheme to use.
• New `.xctool-args` (so we get reasonable pass/fail status from tests in Travis-CI, and so we can double-check the CLI build process locally) specifies the name info, plus some normal stuff (configuration, sdk, arch, and ONLY_ACTIVE_ARCH=NO).
• Added Travis-CI build status to the top of the README.
• Removed the default single failing test.