Pyret IDE error rendering

[jpolitz]

• Implement components for error-display (highlights as prototype)
  • Especially CodeMirror snippet component
  • Also multi-highlighting, fixed highlighting (both modes)
  • Port callbacks for parsing, fetching AST information
  • Stored non-definitions modules for fetching source
• Hook up component creation in compile and parse entry points from runtimeAPI
• Interface with value rendering for nested value display (when necessary)