- State in README.rst and setup.py metainfo that we require Python>=3.5
- Let Travis-CI test against newer versions of Python
- Let instaloader --help show where to report issues
This is a) cooler and b) a requirement for deploying it on PyPI.
It removes need of __all__ shit (which is hard to keep updated), and
allows installing instaloader easily as a global module and executable.
Additionally it removes __init__.py.