Removed env from redirect and changed redirect from method to macro.

Removed `env.redirect` in-favor of `redirect` in-order to make Kemal's
API look more like Sinatra.

Thanks @sdogruyol and @f for introducing me to macros :-).

Binding HTTP::Server to 0.0.0.0

spec/kemal_handler_spec.cr

@@ -187,7 +187,7 @@ describe "Kemal::Handler" do
   it "redirects user to provided url" do
     kemal = Kemal::Handler.new
     kemal.add_route "GET", "/" do |env|
-      env.redirect("/login")
+      redirect "/login"
     end
     request = HTTP::Request.new("GET", "/")
     response = kemal.call(request)