Refactor and fix some docs

spec/log_handler_spec.cr

@@ -0,0 +1,22 @@
+require "./spec_helper"
+
+describe "Kemal::LogHandler" do
+  it "logs to the given IO" do
+    config = Kemal.config
+    io = IO::Memory.new
+    logger = Kemal::LogHandler.new io
+    logger.write "Something"
+    io.to_s.should eq "Something"
+  end
+
+  it "creates log message for each request" do
+    request = HTTP::Request.new("GET", "/")
+    io = IO::Memory.new
+    context_io = IO::Memory.new
+    response = HTTP::Server::Response.new(context_io)
+    context = HTTP::Server::Context.new(request, response)
+    logger = Kemal::LogHandler.new io
+    logger.call(context)
+    io.to_s.should_not be nil
+  end
+end