Support SQLite

[pmcnr-hx]

SQLite doesn't support nested transactions which this project seems to depend on. The project doesn't announce support for SQLite, but it should technically be possible to support it alongside the other Sequelize supported dialects.

SequelizeDatabaseError: SQLITE_ERROR: cannot start a transaction within a transaction
  at Query.formatError (node_modules/sequelize/lib/dialects/sqlite/query.js:348:14)
  at Statement.afterExecute (node_modules/sequelize/lib/dialects/sqlite/query.js:112:29)
  at Statement.replacement (node_modules/sqlite3/lib/trace.js:20:31)
  at Statement.replacement (node_modules/sqlite3/lib/trace.js:20:31)