v0.3.0

appc spec version: v0.7.4

• Sets the PATH environment variable inside of acbuild run commands, instead of
  propagating the variable from the host.
• Copy has been split out into copy and copy-to-dir. copy is for copying a
  given file/directory to a specific path, and copy-to-dir is for copying one
  or more files/directories into a given directory. error.
• The run and end subcommands now contain a check for if .acbuild/target is
  mounted, and will attempt to unmount it before performing their actions.
• The flag --working-dir has been added to the run subcommand, for specifying
  the working directory to run the given command in. This requires systemd >=
  229.
• Added support for passing the begin command a tarball, which when not a valid
  ACI will be used as the starting rootfs for the build.
• Now uses version 0.7.4 of the AppC spec.