Use maintained Docker baseimage

[peterrus]

With the intention of letting test pass so we can work on thumbor-community/aws#147

This base image only (roughly) contains up to date dependencies needed to run test for tc_aws on CircleCI (and locally).

@Bladrak If the CircleCI + Docker Hub setup is still working we should be able to use this together with: thumbor-community/aws#153

[Bladrak]

Aren't we missing opencv from this image? Did the tests pass with it?

[peterrus]

@Bladrak I saw no indication that this docker image was used in Thumbor itself (anymore): https://github.com/thumbor/thumbor/blob/master/.circleci/config.yml#L14

So basically this image is only used for tc_aws as far as I know. So the tc_aws tests did indeed pass when running this image locally (and I suspect it will also pass on CircleCI).

[Bladrak]

Ok let's try it then :)