Zodipy

- Added possibility to mask pixels during an observation 6edfc1aab6e9a85fbe9381071bed855ae7788501 aaa79f20111004606c544443202b10570307b60f b7f1486f70446d98c8e72cd3ae986a9cb07137ef.
- Observation times are now given through three separate keywords (start, stop, step) to the `Zodi` object, 6f79b42c8b9217941ee72e372fb97ff331aabc40 c3e08b43e4a9d59a1f549398e1ba2ee62362ccea.

- Changed input argument types to `Zodi` object 1703eb8.
- Fixed import override 6cbf848.
- Added `__all__`.

- Fix bug where initializing the Zodi interface without any arguments would raise an exception f9da748.