Fixes syntax error in vim script
Fixes artefact typo in the shell script
Implement non-blocking output of the REPL

Fixes a number of weird behavioural bugs
E.g., the output would contain ^@'s because certain file pointers were reset,
and others were not. The alternative was to have all output (also that of old
parses/commands) copied to vim.
Switch to python3
Teach vim how to deal with python