Photonai

- removed investigator, instead we offer the Explorer, a Javascript web application to visualize and analyze the results
- moved photon.neuro module to an own package called photonai_neuro
- updated repository structure, moved tests and examples to root directory
- consistently named the repository photonai everywhere
- included continuous integration pipeline with travis-ci

Starting with this release, you should be able to install PHOTON via pip. Issues with installing the requirements have been resolved. This release includes the PHOTON Investigator to visualize the results.