http: automatically follow redirects.

* Automatically follow redirects (up to 5, return a synthetic 598 error after that).
* Add `put` and `timeout` methods.
* Add tests.

test/unit/danbooru_http_test.rb

@@ -0,0 +1,49 @@
+require 'test_helper'
+
+class DanbooruHttpTest < ActiveSupport::TestCase
+  context "Danbooru::Http" do
+    context "#get method" do
+      should "work for all basic methods" do
+        %i[get put post delete].each do |method|
+          response = Danbooru::Http.send(method, "https://httpbin.org/status/200")
+          assert_equal(200, response.status)
+        end
+      end
+
+      should "follow redirects" do
+        response = Danbooru::Http.get("https://httpbin.org/absolute-redirect/3")
+        assert_equal(200, response.status)
+      end
+
+      should "fail if redirected too many times" do
+        response = Danbooru::Http.get("https://httpbin.org/absolute-redirect/10")
+        assert_equal(598, response.status)
+      end
+
+      should "fail if the request takes too long to connect" do
+        response = Danbooru::Http.timeout(1).get("https://httpbin.org/delay/5")
+        assert_equal(599, response.status)
+      end
+
+      should "fail if the request takes too long to download" do
+        response = Danbooru::Http.timeout(1).get("https://httpbin.org/drip?duration=5&numbytes=5")
+        assert_equal(599, response.status)
+      end
+
+      should "automatically decompress gzipped responses" do
+        response = Danbooru::Http.get("https://httpbin.org/gzip")
+        assert_equal(200, response.status)
+        assert_equal(true, response.parse["gzipped"])
+      end
+
+      should "cache requests" do
+        response1 = Danbooru::Http.cache(1.minute).get("https://httpbin.org/uuid")
+        assert_equal(200, response1.status)
+
+        response2 = Danbooru::Http.cache(1.minute).get("https://httpbin.org/uuid")
+        assert_equal(200, response2.status)
+        assert_equal(response2.body, response1.body)
+      end
+    end
+  end
+end