Merge pull request #58 from aaccomazzi/master

Fixes issue #51
Implement flag to ignore JSON fingerprint when --target-bibcodes is passed in sync mode; references #59; needs testing with connection to classic
Merge branch 'master' of https://github.com/adsabs/ADSimportpipeline
Add optional file-reading in --target-bibcodes with '@' syntax. References #59
Remove confusing argument --bibcode-files. Use instead --target-bibcodes, or change `settings.py` to change the bibcode files.
Test for the existence of args.bibcode before comparing its first element
Tweaked schema, updated tests