Hepdata-lib

Add six as requirement (180)

Fix missing file in tar ball (174)

* Add test for nested file copy
* Improve handling of file copying, fix missing file problem
* Fix return type: tuple instead of generator
* Disable inappropriate pylint warning
* Freeze pylint version

- Implement one-sided uncertainty (169)
* Implement one-sided uncertainty
* Cleanup imports
- Factor out additional resources, add to Table (170)
* Factor out additional resources, add to Table
* Add test
* Add default hepdata_lib reference in Submission additional material.
* remove useless try/except block

- RootFileReader: Allow access to bin labels + small other improvements (https://github.com/HEPData/hepdata_lib/pull/168)

Manually created release to publish recent changes.