Create functional option for ctx.SetCookie

[zeripath]

Allowing func(*http.Cookie) to be passed into the SetCookie call will allow us to extend SetCookie to set the SameSite attribute easily.

(This PR also does some slight cleanup to context.go fixing minor lint issues.)

[6543]

@unknwon can you have a look at it?

it also would cover #206 ... but in a more general way :)

[unknwon]

Thanks for the PR!

Can we also have some tests to cover uses of these helpers?

Likely will be added to here:

macaron/context_test.go

Lines 206 to 212 in d229aed

	Convey("Set and get cookie", func() {
	m.Get("/set", func(ctx *Context) {
	t, err := time.Parse(time.RFC1123, "Sun, 13 Mar 2016 01:29:26 UTC")
	So(err, ShouldBeNil)
	ctx.SetCookie("user", "Unknwon", 1, "/", "localhost", true, true, t)
	ctx.SetCookie("user", "Unknwon", int32(1), "/", "localhost", 1)
	ctx.SetCookie("user", "Unknwon", int64(1))

[6543]

@unknwon It's ready again :)

[unknwon]

Thanks for the follow up!

[unknwon]

https://github.com/go-macaron/macaron/releases/tag/v1.4.0 has been published for this merge.