Add configurable startup logging as a block (#291)

Add overload for Kemal.run with just a block. This removes default logging.

spec/run_spec.cr

@@ -0,0 +1,30 @@
+require "./spec_helper"
+
+describe "Run" do
+  it "runs a code block after starting" do
+    Kemal.config.env = "test"
+    make_me_true = false
+    Kemal.run do
+      make_me_true = true
+      Kemal.stop
+    end
+    make_me_true.should eq true
+  end
+
+  it "runs without a block being specified" do
+    Kemal.config.env = "test"
+    Kemal.run
+    Kemal.config.running.should eq true
+    Kemal.stop
+  end
+
+  it "runs with just a block" do
+    Kemal.config.env = "test"
+    make_me_true = false
+    Kemal.run do
+      make_me_true = true
+      Kemal.stop
+    end
+    make_me_true.should eq true
+  end
+end