Support local webpack

Makefile

@@ -6,10 +6,12 @@ BUILD_OPTIONS = -ldflags "-X main.Version=$(VERSION) -X main.CommitID=$(GIT_COMM
 gotty: main.go server/*.go webtty/*.go backend/*.go Makefile
 	godep go build ${BUILD_OPTIONS}
 
+.PHONY: asset
 asset: bindata/static/js/gotty-bundle.js bindata/static/index.html bindata/static/favicon.png bindata/static/css/index.css bindata/static/css/xterm.css bindata/static/css/xterm_customize.css
 	go-bindata -prefix bindata -pkg server -ignore=\\.gitkeep -o server/asset.go bindata/...
 	gofmt -w server/asset.go
 
+.PHONY: all
 all: asset gotty
 
 bindata:
@@ -47,11 +49,13 @@ js/node_modules/xterm/dist/xterm.css:
 	cd js && \
 	npm install
 
-js/dist/gotty-bundle.js: js/src/*
+js/dist/gotty-bundle.js: js/src/* js/node_modules/webpack
 	cd js && \
-	webpack
-
+	`npm bin`/webpack
 
+js/node_modules/webpack:
+	cd js && \
+	npm install
 
 tools:
 	go get github.com/tools/godep