Adds a few additional dplyr functions to the package imports, in particular: slice, data_frame, and row_number.

Uses the algorithm mentioned at https://stackoverflow.com/a/3943023/2022615 based on the luminance of the background color to determine black or white text. The threshold favored black text in a way that didn't look good with our plots, so I increased the threshold from 0.179 to 0.333.

if printed it will still call animate, but gives the user more flexibility about animation factors (such as times etc)

- Import packages from tidyverse
- Set global imports in zzzz-package.R
- Import pipe and tidyeval
- Update authors
- Downgrade version to 0.0.1.9000
- Change license to MIT
- TODO: Internal package qualifications still needed, e.g. dplyr::row_numbers()

-id1, -id2 work, id1:id2 does not (yet)

this makes it easier to differentiate between the join-related and the (coming) tidyr-related functions that have similar goals

modified union animation and added union_all

intersect/union/setdiff