v0.7.0

• Added --only-code-output option, which writes code output in JSON Lines
  format to stdout as soon as it is available, and does not create a document.
  This is intended for use with Codebraid Preview, so that document previews
  can be updated during code execution.

• Added command-line option --no-execute that disables code execution and
  only uses available cached output.

• Added first-chunk setting executable_opts for passing command-line options
  to the executable that compiles/runs code (#52).

• Setting executable to an executable relative to the working directory (for
  example, ./exec.sh) now functions correctly. Previously, pathlib.Path()
  was used to track executables, but it strips a leading ./.

• Added first-chunk setting args for passing command-line arguments to
  executed code.