Externalizing web assets

mostly to ease editing, but also for practice with file manipulation,
gzipping, base64'ing, etc.

conway/Makefile

@@ -4,18 +4,21 @@ TARGETS := \
 	$(LIBS) \
 	github.com/meatballhat/box-o-sand/conway/conways-game-of-life
 
-all: deps build
+all: test
 
-build: test
+test: build
+	go test -x -v -test.parallel=4 $(LIBS)
+
+build: web_assets.go deps
 	go install -x $(TARGETS)
 
+web_assets.go: $(wildcard web_assets/*.*)
+	./gen-web-assets
+
 clean:
 	go clean -x -i $(TARGETS)
 
-test:
-	go test -x -v -test.parallel=4 $(LIBS)
-
 deps:
-	go get -x $(TARGETS)
+	go get -n -x $(TARGETS)
 
 .PHONY: all build clean deps test