WIP: Astrocyte 0.4.0

Please fill in the appropriate checklist below (delete whatever is not relevant). These are the most common things requested on pull requests (PRs).

PR checklist

• This comment contains a description of changes (with reason)
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated
• CHANGELOG.md is updated
• README.md is updated
• nextflow.config pipeline version updated

• Close issue
  Closes #41 Closes #42

/cc @ghenry @venkat.malladi