v0.0.4:
- check_correctness also runs in a separate process
- lint counter function added (count_lints)
- run_tuner asks for permission before installation
- generate thumbnails uses anonymous filenames

v0.0.3:
- render_one runs the student script in a separate process, avoiding the need 
  to check the user workspace, or to reset search paths.
- testthat chunks are no longer used in the solution templates. This prevents 
  any problems if testthat format is modified.
  
v0.0.2:
- render_one allows one to skip correctness checks by setting soln_stuff to be 
  NA.

v0.0.1.2:
- check_rmd just checks for chunks, uses extract_chunks directly
- fh helper to detect for nested for loops added.
- bug fix for lang_2_tree, when a function definition had NULL as a default
  argument.

v0.0.1.01:
- If the solution template did not generate all the scalars it claimed to,
  render_one( ) will fail, because it checks for the mode of the scalars
  from the student environment against the mode of the scalars in the solution
  environment. This has been fixed by running this check when
  populate_soln_env( ) is called.

v0.0.0.9008:
- tuner app will now take in a list of lints, and output dataframe can
  be controlled by specifying the columns to drop.

v0.0.0.9007:
- TreeHarp constructors updated to work with output of class( ) from R v4.0.0.

v0.0.0.9005:
- testthat output handles tests such as setequal (which actually runs two tests)
- max run time added to render_one
- with the realisation that non-test-named files can be put in tests/, more tests added.

v0.0.0.9004:
- testthat output is parsed better
- scalars must be atomic, they are also checked against the template objects
- more solution templates added.

v0.0.0.9003:
- hooks are renamed to be autoharp.objs and autoharp.scalars.
- solution objects, scalars to keep, filename  are stored as hidden objects in the
  environments.
- testthat chunks and static code chunks can both be in the same solution template.
