EvanOdell/mnis: v0.2.6

Now accepts dates as character values in "YYYY-MM-DD" format, and objects of class Date, POSIXt, POSIXct, POSIXlt or anything else than can be coerced to a date with as.Date().

Fixed bugs on mnis_joined_between to return full, proper tibble.

Dropped parameter 'joined_since' from mnis_all_members, in favour of mnis_joined_between.

Tidied up code in mnis_reference functions.

Fixed bug in mnis_party_state which produced an error if not using the current system date.

Added optional 'tidy_style' parameter, allowing users to decide which style "snake_case", "camelCase" and "period.case" they want variable names to be in, if 'tidy'==TRUE. mnis 0.2.5