Geoana

This update cleans the dependencies for running geoana, as both ipywidgets and jupyter were not required to run the package. There are also updates for new website names within the documentation

Magnetic pole class for simulating monopole response in magnetic survey.


Used in

https://mybinder.org/v2/gh/geoscixyz/gpgLabs/master?filepath=Notebooks%2FMagneticDipoleApplet.ipynb

- originally from pr 9
- commits by: lheagy, sgkang
- review from: sgkang

Magnetostatic Vector Potentials
- add vector potentials for a dipole and loop source in `geoana.em.static`
- add example for usage
- associated testing

Repo Maintenance
- improve README, existing docs
- test using anaconda installation
- update gitignore
- add sphinx gallery for docs

- from PR 6
- commits from lheagy
- review from rowanc1, sgkang

Updates
- first pass at FDEM and TDEM dipoles
- upgrades to oskar code to be consistent with properties upgrades
- clean up the docs
- testing on appveyor