EM Paper
- from PR 614. Commits from: sgkang, lheagy
- bookpurnong inversion examples from the EM paper
- first pass at a grounded source implementation for `TDEM.Problem3D_e`
![image](https://user-images.githubusercontent.com/6361812/27650679-72580eac-5bea-11e7-8c97-0cfc69bc22b7.png)
MT tutorial
- from PR 611, 615, 619. Commits from: thast, sgkang, lheagy. Reviews from: lheagy, rowanc1
- 1D MT layered earth analytic
- updates to the saving directive to output each component of the regularization, option to save the text file or not
- plot the Tikhonov curve with the directive
![image](https://user-images.githubusercontent.com/6361812/27650820-03571182-5beb-11e7-80cc-5f730d8e95a8.png)
Testing and Deploy of Documentation
- from PR 618, 620. Commits from lheagy, Review from rowanc1
- cache the docs and examples so that they are only tested on changes rather than testing every time
Minor changes
- update the default for `surface2ind_topo` to be `nearest`. fourndo, review from thast