v0.5.2

• add some Ruby extension prefixes: -, _, and 0, and they work like so:
  strftime('%-d') // => "7"
strftime('%_d') // => " 7"
strftime('%0d') // => "07"
• fix padding the day-of-year in %j
• add a minified version of the code to the repo for easy distribution with some package managers