Add CPC codes from single reference products during ecospold2 import.
0.7.8
Merged [Pull Request 5](https://bitbucket.org/cmutel/brightway2-io/pull-requests/5/bug-fix-for-simapro-imports) to fix some SimaPro import issues. Thanks Benjamin Portner!
0.7.7
0.7.6
* Exit Excel importer early if no data found * Handle all columns cutoff in Excel importer * Fix Gephi exporter for ecoinvent v3
0.7.5
* Fix 59: Importing ecospold1 fails due to unset variable in extractor
0.7.4
Fix location updating bug preventing clean import of ecoinvent 2.2