Use base docker image for CI builds

[springmeyer]

After we move to circle (#536) we should start using a consistent base docker image for building binaries on linux (@mapbox/core-tech will provide and maintain this base image). We should make sure this docker image has at least libstdc++-4.8-dev available to support c++11 out of the box, but potentially using a more recent version (or making it possible to toggle) could be desirable, so this will take some thought.

/cc @kkaefer

[kkaefer]

Could be good to prove them before migrating to Circle CI ;)

As a reminder, https://github.com/mapbox/jni.hpp/tree/circleci-images also exists (though I'm not sure it's the approach we should take for this image).