Add example tags again

This reverts commit 7a1d63fb02.

.travis.yml

@@ -31,8 +31,8 @@ before_script:
   - sleep 3
 
 script:
-  - go build -v ./...
-  - gopherjs build -v github.com/hajimehoshi/ebiten/examples/blocks
+  - go build -tags example -v ./...
+  - 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

examples/2048/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/additive/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/airship/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/alphablending/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/audio/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/blocks/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/font/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/gamepad/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/hsv/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/hue/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/infinitescroll/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/keyboard/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/life/main.go

@@ -21,6 +21,8 @@
 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
+// +build example
+
 package main
 
 import (

examples/masking/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/mosaic/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/noise/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/paint/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/pcm/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/perspective/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/piano/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/rotate/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/sinewave/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/sprites/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (

examples/windowsize/main.go

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build example
+
 package main
 
 import (