ggdag 0.2.2

Added vdiffr tests, as well as a basic test file for every .R file. (#27)
Updated roxygen2 version (#29)
Fixed bugs in dag_paths() and geom_dag_edges_fan() (#31)
Removed use of use_defaults() ggproto method in GeomDAGEdge (#33)
Use ggplot2::expansion() instead of expand_scale() when ggplot2 version is at least 3.3.0 and removed local version of expand_scale() (#34)

ggdag 0.2.1

Fixed bug in ggdag_collider() where the aesthetics were flipped for the colors but not the labels (issue #15, b72e34b)
Used as.character.default() directly for working with characters to avoid dispatch error when the formula.tools package is attached (issue #17, 0f32bb4)

Fixed compatibility issue with ggraph 2.0.0 by changing to strength parameter in curved geoms
Fixed join bug in node_equivalent_class() that didn’t account for the way dagitty returns DAGs with no direction
Fixed join bug in node_equivalent_class() that didn’t check to node
Implemented is_false() to avoid dependency on R 3.5.0
improved edge lengths
add {} to adjustment set names to reflect convention
Set nodes to be unstyled by default
Changed default themes and scales to be more like base ggplot2
Added a NEWS.md file to track changes to the package.