Barnhark/make 800 variant docs and tests

[kbarnhart]

Addresses #49 Not yet done.

[coveralls]

Pull Request Test Coverage Report for Build 406

• 154 of 160 (96.25%) changed or added relevant lines in 24 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+15.9%) to 67.887%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
terrainbento/derived_models/model_012_basicHyTh.py	0	1	0.0%
terrainbento/derived_models/model_200_basicVs.py	1	2	50.0%
terrainbento/derived_models/model_202_basicThVs.py	1	2	50.0%
terrainbento/derived_models/model_208_basicDdVs.py	1	2	50.0%
terrainbento/derived_models/model_210_basicHyVs.py	1	2	50.0%
terrainbento/derived_models/model_600_basicSaVs.py	1	2	50.0%
<!--	Total:	154	160	96.25%	-->

Totals
Change from base Build 327:	15.9%
Covered Lines:	1317
Relevant Lines:	1940

---

💛 - Coveralls

[kbarnhart]

@gregtucker @Glader011235 could you take a look at the main docstring for model 800? A lot of it will be duplicated to the other 800 variants (e.g. the parts about multiple layers, smoothing, using elevation instead of depth).

Feel free to commit revisions directly to this branch.

Thanks!

[gregtucker]

Looks good to me

[kbarnhart]

This doesn't have full tests for 808, 810, 840, 842, A00, or C00 yet, but I've made quite a few changes and want to bring it into master.

passes on travis, so I'm merging.