Brightway2

* BREAKING CHANGE: Graph traversal was reworked, and some functionality for interpreting the output was moved to `bw2analyzer`.
* BREAKING CHANGE: Deleted `SimpleRegionalizedLCA` class. Regionalization will be provided in bw2regional.
* BREAKING CHANGE: Deleted initial sensitivity work, moved for now to branch, as it was not yet usable.
* FEATURE: Much better and more thorough documentation.
* FEATURE: Improved testing and test coverage

* Change `import_ecoinvent_release` to allow patching existing biosphere databases

* Fix missing import from dev24
* Some documentation improvements

* [227 Add `import_ecoinvent_release` utility](https://github.com/brightway-lca/brightway2-io/pull/227)
* [222 Move `KEYS` variable to function header](https://github.com/brightway-lca/brightway2-io/pull/222)
* [219 Don't apply set_`biosphere_type` twice](https://github.com/brightway-lca/brightway2-io/pull/219)

* Use bw2data for cache filepath
* Bunch of small issue fixes
* [207 Fixed float parsing errors](https://github.com/brightway-lca/brightway2-io/pull/207)
* [213 Reparametrize lognormals for ecospold2 imports](https://github.com/brightway-lca/brightway2-io/pull/213)

* Pinned dependencies to fix environment problems