Use sql-mode's font-lock for checking

Note that this requires a sql-mode buffer. This change also keeps
`sqlup-keywords' for now as they're necessary for caps-ing a region.
Release 0.3.0

* Use list of SQL keywords provided by sql-mode

Merge branch 'feature/use-font-lock-keywords' of github.com:jahkeup/sqlup-mode.el into jahkeup-feature/use-font-lock-keywords

* 'feature/use-font-lock-keywords' of github.com:jahkeup/sqlup-mode.el:
  Use sql-mode's font-lock for checking

Conflicts:
        sqlup-mode.el