Breaking changes
Python 2 compatibility removed
Removing the Python 2 compatibility layer allows for much cleaner and more compact code, and the use of some components from the in-development Brightway version 3 libraries.
Background changes
Use of `bw_processing`
We now use [bw_processing](https://github.com/brightway-lca/bw_processing) to create processed arrays and magic constants.
Smaller changes
* Merged [PR 81](https://github.com/brightway-lca/brightway2-io/pull/81), SimaPro mappings for ecoinvent 3.4. Thanks PascalLesage
* Merged [PR 80](https://github.com/brightway-lca/brightway2-io/pull/80), SimaPro mappings for ecoinvent 3.5. Thanks PascalLesage
* Merged [PR 82](https://github.com/brightway-lca/brightway2-io/pull/82), fix ecoinvent versus SimaPro different signs of waste treatment processes. Thanks PascalLesage