Add the bundling of CI secrets into Makefile or something

[tintinnabulate]

Currently secrets.tar.enc is created manually from commandline - it would be nice to create this in the Makefile, or even nicer, by a git pre-commit hook, so that it is ready in time continuous integration test suite.

[tintinnabulate]

Implementing this will prevent build failures such as #67.

[tintinnabulate]

$ sudo gem install travis
$ firefox https://github.com/settings/tokens # generate new token
$ travis login --org --github-token <token>
$ tar cvf secrets.tar config.json fanjoula.json
$ travis encrypt-file secrets.tar
$ git add secrets.tar.enc