Port here the classes from the legacy fatiando package #1
Description
The classes that did the modeling were implemented in a branch of the fatiando package and never merged into the main project. This is a link to the code:
https://github.com/fatiando/fatiando/tree/wavefd/fatiando/seismic/wavefd
We need to move the classes to Tremelique and make sure they work under Python 3. This shouldn't be a big issue. The Acoustic class is already here.