fix scanning into enums

[joshuarubin]

The enum issue may only be because I am using a column with an array of enums.
Also, Scan() can panic if it's not passed a []byte. I can have it return an error instead, but that requires importing fmt or errors, wasn't sure if it was worth the trouble. Thoughts?

[kyleconroy]

If this is happening when you're scanning into an array of enums, can you add a test case for that? It's a bit involved, but you can add a new query to the ondeck package.

[joshuarubin]

OK, I've added a test that failed before this change.

[kyleconroy]

Thanks! I know update the db_test.go file isn't the easiest. Really appreciate adding the tests.

[joshuarubin]

Thanks!