Reduce duplication of testing.T argument

[eberkund]

It would be nice if the next version used a syntax similar to stretchr/testify. Since t is passed in to New() we shouldn't need to pass it in again for each assertion.

See this example from stretchr/testify:

package yours

import (
  "testing"
  "github.com/stretchr/testify/assert"
)

func TestSomething(t *testing.T) {
  assert := assert.New(t)

  // assert equality
  assert.Equal(123, 123, "they should be equal")

  // assert inequality
  assert.NotEqual(123, 456, "they should not be equal")

  // assert for nil (good for errors)
  assert.Nil(object)

  // assert for not nil (good when you expect something)
  if assert.NotNil(object) {

    // now we know that object isn't nil, we are safe to make
    // further assertions without causing any errors
    assert.Equal("Something", object.Value)
  }
}

For goldie it would look like this:

func TestExample(t *testing.T) {
    recorder := httptest.NewRecorder()

    req, err := http.NewRequest("GET", "/example", nil)
    assert.Nil(t, err)

    handler := http.HandlerFunc(ExampleHandler)
    handler.ServeHTTP()

    g := goldie.New(t)
    g.Assert("example", recorder.Body.Bytes()) // notice lack of `t` arg here.
}

If there is interest, I would be happy to make a PR.