Remove nodejs dependency

Makefile

@@ -194,15 +194,8 @@ $(MAVEN_DIR)/pom.xml : $(JEKYLL_SRC_DIR)/_data/versions.yml $(JEKYLL_SRC_DIR)/_d
 	fi
 
 .PHONY : serve
-serve : ws all
-	ws -d $(CURDIR)/$(JEKYLL_DIR)/_site
-
-.PHONY : ws
-ws :
-	@if ! which $@ >/dev/null 2>/dev/null; then \
-		echo "ws is not installed, install with 'npm install -g local-web-server'" 2>&1; \
-		exit 1; \
-	fi
+serve : all
+	ruby -r webrick -e "s = WEBrick::HTTPServer.new(:Port => 8080, :DocumentRoot => '$(CURDIR)/$(JEKYLL_DIR)/_site'); trap('INT') { s.shutdown }; s.start" 
 
 .PHONY : publish
 publish : all