Instaseis

- Fixed problem which modified cached values in certain circumstances (see 76).

- Updating all copyright notices.

- Dropping support for Python < 3.7.
- Updated to support the latest version of all dependencies, especially
`tornado` and `pytest`.

- Updated to support the latest versions of `ObsPy` and `tornado`.
- Now uses the NMSOP recommended definition of the moment magnitude.
(see 58)
- Stable finite element mappings also for local/regional scale databases.
(see 61)
- Source time functions for force sources (see 49).
- Some other small distribution fixes and improved error messages.

- Closing sockets after each test case ran (see 48).
- GUI can now display map backgrounds for many planets/moons in the solar
system. (see 54).
- Forcing installation of `geographiclib` (see 57).
- Setting `CMPINC` and `CMPAZ` headers in SAC files for the server routes.

- Compatibility with `numpy` 1.12