TODO - Evcxr — ContextQMD

If we get an error in generated code, tell the user a command to start investigation.
Try using a workspace instead of setting target directory, copying Cargo.lock etc.
Consider adding a crate to aid in interfacing with Evcxr.
Compile item-only crates as rlibs instead of dylibs to avoid having them get recompiled next line.
Tab completion. Perhaps bring up RLS and query it to determine completion options.
Allow history of session to be written as a crate.
Allow history of session to be written as a test.
Allow a block of code to extend over multiple lines.
Allow customization of colors.
Allow some form of startup scripting - or at least a way to load the crate from the working dir.
Automatically make all items pub
- Probably not really practical while we can't make use of spans from syn.
Investigate lack of warning: function cannot return without recurring
- Probably we're not currently showing any warnings (if compilation succeeds). Perhaps we should.
Consider emitting compilation errors as HTML and adding an "explain" link.