fix for double quoting cast

[reygoch]

@tomjaguarpaw I've implemented the fix recommended in #197 #issuecomment-371183995. My code works now and user is properly inserted.

[tomjaguarpaw]

This is an interesting test failure. The change I suggested writes array types as, e.g., "float8[]" when it should be "float8"[]. I will think about the best way to address this. In the meantime feel free to keep using this branch with the change unless you need arrays.