Fix for issue #38

[kav]

Args was passed to bwipp instead of generated opts

[metafloor]

Thanks. You must be using the toBuffer() interface directly. Need to add a test case for that.

[kav]

No, I was having the same issue the poster of the orginal issue was. Set up a new express app, wire bwip to a route, visit that route with barcode query string params, see error.