Harness for 7 chokes on the "gotcha"

[ribasushi]

Related to #16, if I omit the pass-by-reference:

func ( u User ) SetUsername ( uname string ) {      // <--- * missing here
  u.username = username(uname)
}

Then the error is yet again

$ go test
--- FAIL: TestMethods (0.00s)
panic: interface conversion: interface {} is user.username, not string [recovered]
        panic: interface conversion: interface {} is user.username, not string

goroutine 5 [running]:
testing.tRunner.func1(0xc4201240f0)
        /usr/lib/go-1.10/src/testing/testing.go:742 +0x29d
panic(0x687ce0, 0xc420062880)
        /usr/lib/go-1.10/src/runtime/panic.go:502 +0x229
github.com/stretchr/testify/assert.diff(0x66f4c0, 0x70bd60, 0x66f4c0, 0xc420010c80, 0x0, 0x0)
        /home/goclass/go/src/github.com/stretchr/testify/assert/assertions.go:1352 +0x453
github.com/stretchr/testify/assert.Equal(0x70d260, 0xc4201240f0, 0x66f4c0, 0x70bd60, 0x66f4c0, 0xc420010c80, 0xc420059e48, 0x1, 0x1, 0xc420010c80)
        /home/goclass/go/src/github.com/stretchr/testify/assert/assertions.go:338 +0x26a
github.com/stretchr/testify/assert.(*Assertions).Equal(0xc420047dc8, 0x66f4c0, 0x70bd60, 0x66f4c0, 0xc420010c80, 0xc420047e48, 0x1, 0x1, 0x40d9f301)
        /home/goclass/go/src/github.com/stretchr/testify/assert/assertion_forward.go:129 +0xca
github.com/autarch/intro-to-go-class-exercises/7-basic-oo/user.TestMethods(0xc4201240f0)
        /home/goclass/go/src/github.com/autarch/intro-to-go-class-exercises/7-basic-oo/user/user_test.go:21 +0x48a
testing.tRunner(0xc4201240f0, 0x6ec5e0)
        /usr/lib/go-1.10/src/testing/testing.go:777 +0xd0
created by testing.(*T).Run
        /usr/lib/go-1.10/src/testing/testing.go:824 +0x2e0
exit status 2
FAIL    github.com/autarch/intro-to-go-class-exercises/7-basic-oo/user  0.008s

[autarch]

Fixed in stretchr/testify#622

Hopefully this will get merged before the next time I do this class.

[autarch]

Fixed by updating the deps for the class exercises.