Fix files for 'example' tag

.travis.yml

@@ -32,7 +32,7 @@ before_script:
 
 script:
   - go build -tags example -v ./...
-  - gopherjs build -tags example -v github.com/hajimehoshi/ebiten/examples/blocks
+  - gopherjs build --tags example -v github.com/hajimehoshi/ebiten/examples/blocks
 
 # Give up testing on Travis CI because of X error
 # https://travis-ci.org/hajimehoshi/ebiten/jobs/107404013

_docs/index.tmpl.html

@@ -58,10 +58,12 @@ pre {
   {{- end}}
 </p>
 
-<h2>Execute the example</h2>
+<h2>Execute the examples</h2>
 <pre><code>:; go get github.com/hajimehoshi/ebiten
 :; cd $GOPATH/src/github.com/hajimehoshi/ebiten/examples
-:; go run rotate/main.go</code></pre>
+:; go run -tags example rotate/main.go</code></pre>
+
+<p>Note that you need to specify <code>example</code> tag.</p>
 
 <h2>Getting Started</h2>
 

examples/README.md

@@ -0,0 +1,8 @@
+# Exacute the examples
+
+```sh
+:; cd $GOPATH/src/github.com/hajimehoshi/ebiten/examples
+:; go run -tags example rotate/main.go
+```
+
+Note that you need to specify `example` tag.

examples/_server/main.go

@@ -63,7 +63,7 @@ func createJSIfNeeded(name string) (string, error) {
 	}
 	if (err != nil && os.IsNotExist(err)) || time.Now().Sub(stat.ModTime()) > 5*time.Second {
 		target := "github.com/hajimehoshi/ebiten/examples/" + name
-		out, err := exec.Command("gopherjs", "build", "-o", out, target).CombinedOutput()
+		out, err := exec.Command("gopherjs", "build", "--tags", "example", "-o", out, target).CombinedOutput()
 		if err != nil {
 			log.Print(string(out))
 			return "", errors.New(string(out))