Add Dockerfile.

Dockerfile

@@ -0,0 +1,24 @@
+FROM alpine:3.4
+
+RUN apk add --no-cache g++ make go
+
+
+RUN mkdir -p /tmp/go-lbiwebp
+COPY Makefile /tmp/go-libwebp/Makefile
+
+ENV LIBWEBP_PREFIX="/usr/local" \
+    LIBWEBP_VERSION="0.5.0"
+RUN cd /tmp/go-libwebp && make libwebp
+
+ENV GOPATH="/go" \
+    WORKDIR="/go/src/github.com/harukasan/go-libwebp" \
+    PATH="/go/bin:/usr/local/go/bin:$PATH" \
+    CGO_CFLAGS="-I /usr/local/include"  \
+    CGO_LDFLAGS="-L /usr/local/lib" \
+    LD_LIBRARY_PATH="/usr/local/lib:$LD_LIBRARY_PATH"
+
+RUN mkdir -p $WORKDIR
+VOLUME $WORKDIR
+WORKDIR $WORKDIR
+
+CMD ["make", "test"]