Middleware ordering (#236)

Improve and correct request middleware

 Request -> Middleware -> Filter -> Route

spec/handler_spec.cr

@@ -0,0 +1,30 @@
+require "./spec_helper"
+
+class CustomTestHandler < HTTP::Handler
+  def call(env)
+    env.response << "Kemal"
+    call_next env
+  end
+end
+
+describe "Handler" do
+  it "adds custom handler before before_*" do
+    filter_middleware = Kemal::Middleware::Filter.new
+    filter_middleware._add_route_filter("GET", "/", :before) do |env|
+      env.response << " is"
+    end
+
+    filter_middleware._add_route_filter("GET", "/", :before) do |env|
+      env.response << " so"
+    end
+    add_handler CustomTestHandler.new
+
+    get "/" do |env|
+      " Great"
+    end
+    request = HTTP::Request.new("GET", "/")
+    client_response = call_request_on_app(request)
+    client_response.status_code.should eq(200)
+    client_response.body.should eq("Kemal is so Great")
+  end
+end