0.2.2 Release

This release fixes a bug in version 0.2.1 where an exception 'TypeError: can only concatenate str (not "bytes") to str' was raised when the hepdata_doi option is passed as an optional argument to the convert function, as done in the code for the HEPData web app. As with version 0.2.1, it is recommended to use this release with the Docker image hepdata/hepdata-converter:0.2.0.