YAML encoding

 * leave it to PyYAML to determine file encoding (#39)

YAML!

 * reads in YAML format as well as sqlite (#36)
 * fixes rows with null or missing primary key values (#37)

merge bugfixes

 * eliminated single-character company names/keys (#33)
 * use canonical company/brand when building category table (#34)
 * output now uses NFC unicode normalization, not NFKD (#32)
 * fix "a/s" (#30) and "Pvt Ltd" (#12) company suffixes
 * custom corrections: make "Pet" and "Restaurant" categories plural (#9)

select_groups()

 * fix severe bug in select_groups() that silently dropped data (#27)

Install dependencies

 * setup.py includes dependencies in install_requires

Initial release