Add the --sort and --reverse-sort command line args
Add the --heading and --reverse-heading
Warn if multiple citations map to the same object
Allow any citeable object to have ps, pdf, abstract, category, subcategory fields
Add "month" to articles
Add http field to all citeable objects
Don't warn about overrides when the overridden fields match
Add the "homepage" style
Add URLs to Homepage style
Merge git://github.com/rescrv/crosstex

* git://github.com/rescrv/crosstex:
  Add URLs to Homepage style
  Add the "homepage" style
  Don't warn about overrides when the overridden fields match
  Add http field to all citeable objects
  Add "month" to articles
  Allow any citeable object to have ps, pdf, abstract, category, subcategory fields
  Warn if multiple citations map to the same object
  Add the --heading and --reverse-heading
  Add the --sort and --reverse-sort command line args