Implementing BibTex parsing directly from arXiv.
Merge branch 'appkit' into arxiv

* appkit:
  Search for PyObjC module in the system python path, else asks to install it from the webpage.
Working arXiv parsing
Better author parsing
Properly handle arXiv mirrors in ArXivURL
List of strings output in BibDesk.__call__ and fixed arXiv identifier parsing from ADS page.
Merge branch 'appkit' into arxiv

* appkit:
  List of strings output in BibDesk.__call__ and fixed arXiv identifier parsing from ADS page.
Clean numberOfItems usage
arxiv branch is stable