Better Error Messages

[jalextowle]

Description

Like any compiler, solfix will be expected to report any errors that it finds as it processes the input. At the moment, our parser is bearing the brunt of the responsibility for reporting these errors (as it should), and it is not producing a stack trace.

Acceptance Criteria

• Error messages have a stack trace
• Error messages include the line in which the error occurred

Bonus

• Switch to continuation passing style for errors in the parser (might be required for the above)