SQL syntax highlighting with CodeMirror

[tomdyson]

Addresses #13

Future enhancements could include autocompletion of table and column names, e.g. with

extraKeys: {"Ctrl-Space": "autocomplete"},
hintOptions: {tables: {
      users: ["name", "score", "birthDate"],
      countries: ["name", "population", "size"]
    }}

(see https://codemirror.net/doc/manual.html#addon_sql-hint and source at http://codemirror.net/mode/sql/)

[simonw]

This is exactly what I was after, thanks!