upgrade to 2.0.0
split Date object into multiple traits: MonthOps / WeekOps and YearOps
change Weekday to DayOfWeek
DateRange now support step and holiday
rename Calendar to HolidayRule, use weekends instead of WeekendCalendar
try to use implicit conversions to construct PositionOfMonth / PositionOfYear
complete locator related DSL
add conversion logics from locator to pom / poy
some clean ups
port DateRange generation to existing test cases
migrated all sequence related tests to DateRange
decouple from Lamma.sequence
remove unused param Holiday from Lamma.sequence
add language.postfixOps operator
remove language.postfixOps import and add -language:postfixOps in build.sbt
clear java warnings
refactor DateRange to use new Pattern to recur dates
refactor DateRange to use new Pattern to recur dates
some cleanup on deprecated codes
refactor Locator + tests