# Functions
CopyDir copies a directory and all of its contents to the destination directory.
CopyFile copies a file from a source to a destination.
Critical will print a message to os.Stderr unless DEBUG has been set, in which case panic will be called instead.
IsVersion returns whether str is a valid version number.
JoinErrors concatenates the elements of errs to create a single error.
TempDir joins the provided directories and prefixes them with the Sia testing directory.
VersionCmp returns an int indicating the difference between a and b.
# Variables
SiaTestingDir is the directory that contains all of the files and folders created during testing.