Currently only used for setting global text and title font sizes, but can be extended to other options that we may wish to set for more than one plot. For fonts, we now provide `set_font_size()` that can be used to set text and title sizes across all subsequent animations. Includes internal getter functions get_{text|title}_size().

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

Incorporate #5

modified union animation and added union_all

intersect/union/setdiff