Terracotta

New features:
- `/compute` API endpoint to do band math on-the-fly
- Compressed internal tile cache by panakouris

Bug fixes:
- Bump to recent versions of apispec, cachetools, flake8
- Supplying an explicit color map now works as expected
- Fixed broken colormaps

- Overhaul nodata handling
- Add documentation
- Add types to client app
- Fix some tile alignment bugs
- Explicit colormaps now accept RGBA tuples
- Fix some bugs in `optimize-rasters`
- Faster lazy loading support
- Fix some bugs when using the `limit` keyword for `get_datasets`

This release introduces some breaking changes in the Terracotta API and deployment workflow.

Changes

- Added a Zappa callback that ensures consistency of settings and remote database before deployment.
- The Terracotta version used to create a database is now added to the database and checked on connection.
- Terracotta will now warn when calling `driver.insert` on a raster file that is not a cloud-optimized GeoTiff.
- We now support proper logging, including logging to a file.
- Preview images for datasets can be requested via `/singleband/{keys}/preview.png` and `/rgb/{keys}/preview.png`.
- The returned tile size is now configurable from the URL for both `/singleband` and `/rgb`.
- The preferred Zappa settings format is now TOML.
- It is now possible to add a plaintext description of the keys in a Terracotta deployment. The response format of `/keys` is changed to

json
[
{
"key": "key_name",
"description": "key description"
}
]


where `description` is optional.
- Various optimizations and bug fixes.

Changes:

- `/legend` API endpoint renamed to `/colormap`
- Removed `/colormaps` API endpoint
- More performant convex hull computation to speed up ingestion in some cases
- `/colormap` is now properly covered by tests that ensure consistency with images returned by `/singleband`
- `/singleband` now accepts a `explicit_color_map` argument that forces Terracotta to preserve pixel values (e.g. when serving categorical data)
- Added a recipe to serve categorical data to README

First production-ready version of Terracotta.