Epic: read/write control

[nedtwigg]

• Convert ArrayMap to collections.abc #4
• Port TypedPath #23
• Port CommentTracker #25
• recordCall and CallStack/CallLocation #35
• Port WriteTracker and DiskWriteTracker #37
• InlineWriteTracker #43

[nedtwigg]

• Note: InlineWriteTracker is currently blocked on Creating SourceFile #20
• But that's okay, after DiskWriteTracker is done, you could start selfie-runner-pytest, and do full integration testing on CommentTracker.