elsevier_package: various fixes

* Encodes unicode objects to str.

* Fixes imports.

* Fixes on reference harvesting.

* Fixes error handling.

Signed-off by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
Merge pull request #14 from GiorgosPa/elsevier

elsevier_package: encodes unicode objects to str
elsevier_package: change FFT argument

* Changes the FFT argument to $o to uppercase HIDDEN.

Signed-off-by: Jan Aage Lavik <jan.age.lavik@cern.ch>