By default spec-kemal still not depending on kemal-session, but if you
require "spec-kemal/session", "kemal-session" dependency must be added
to shard.yml.
*How to use*
```
require "spec-kemal/session"
it "handles sessions" do
get "/session_var" do |env|
env.session.string?(env.params.query["key"]) || "not found"
end
with_session do |session|
session.string("hey ho!", "let's go! 🎸")
get "/session_var?key=hey+ho!"
response.body.should eq("let's go! 🎸")
end
end
```
