Release blank / nonblank model

[ejm714]

Adds a new official model: blank_nonblank. This was trained on both african forest and european data.

Additional changes:

• lower cases labels in provided csv to improve matching with default model labels

Outstanding:

• [x] documentation
• [x] additional validation for training this model -> see discussion in https://github.com/drivendataorg/pjmf-zamba/issues/130

Closes https://github.com/drivendataorg/pjmf-zamba/issues/130

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[codecov-commenter]

Codecov Report

Merging #228 (2229139) into master (2a4e9fc) will decrease coverage by 0.0%. The diff coverage is 100.0%.

:exclamation: Current head 2229139 differs from pull request most recent head ad1e16c. Consider uploading reports for the commit ad1e16c to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #228 +/- ## ======================================== - Coverage 87.0% 87.0% -0.1% ======================================== Files 29 28 -1 Lines 1937 1931 -6 ======================================== - Hits 1686 1680 -6 Misses 251 251 ``` | [Impacted Files](https://codecov.io/gh/drivendataorg/zamba/pull/228?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=drivendataorg) | Coverage Δ | | |---|---|---| | [zamba/models/config.py](https://codecov.io/gh/drivendataorg/zamba/pull/228/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=drivendataorg#diff-emFtYmEvbW9kZWxzL2NvbmZpZy5weQ==) | `96.7% <100.0%> (+<0.1%)` | :arrow_up: | | [zamba/\_\_init\_\_.py](https://codecov.io/gh/drivendataorg/zamba/pull/228/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=drivendataorg#diff-emFtYmEvX19pbml0X18ucHk=) | | |

[ejm714]

@pjbull this is ready for review. You'll want to read through this issue as well which tries to capture the implications of releasing a binary model on our other configuration options.

[ejm714]

@pjbull I removed the number of models count and left a comment about the slowfast model (IMO nothing to do here, if we want different behavior, let's file an issue and do that separately). Ready for another look