2.0.0

Forked from 1.0.0

• Moved factories to the Calendar class
  • Date::create() -> Calendar::create()
  • Date::parse() -> Calendar::parse()
  • Date::fromDateTime() -> Calendar::fromDateTime()
  • Date::parseDateTimeString() -> Calendar::parseDateTimeString()
  • Added alias fromString() for parse()
• Renamed Date::createJulianDay() to Date::createFromJulianDay()
• Added Julian calendar