elsevier_package: print function and ext_link fix

* Uses print as a function for future Python 3 compatibility.

* Fixes problem with ext_link when it sometimes was None.

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

* Converts allcaps names to first letter capital
  and rest in lower case.

Signed-off by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
aps_package: various fixes

* Fixes affiliation harvesting.

* Adds the page range after pp in unstructered text.

* Uses subfield 't' instead of 'q' for book titles.

* Fixes the year harvesting.

Signed-off by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
Merge pull request #20 from GiorgosPa/pos_package

pos_package: updates naming capitalization
Merge pull request #21 from GiorgosPa/aps_package

aps_package: various fixes
elsevier_package: adds missing year in references.

Signed-off by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
Merge pull request #23 from GiorgosPa/elsevier

elsevier_package: adds missing year in references.
springer_crawler: adds new module

* to crawl from Springer web pages.

Signed-off by: Georgios Papoutsakis <georgios.papoutsakis@cern.ch>
ftp_utils: adds a module to handle ftp downloads.

Signed-off by: Georgios Papoutsakis<georgios.papoutsakis@cern.ch>
Merge pull request #24 from GiorgosPa/ftp_utils

ftp_utils: adds a module to handle ftp downloads.
Merge pull request #22 from GiorgosPa/springer

springer_crawler: adds new module
elsevier_package: affiliation warning improvement

* Improves the warning of multiple implicit affiliations to
  not generate an error on concatenation.

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

* Adds support for simple XML detection in the APS converter. Raises
  new ApsPackageXMLError should the given XML be of a non-JATS format.

* For performance, ApsPackage allows client to pass pre-defined
  journal mappings.

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