add end-to-end tests

tests/Dockerfile

@@ -0,0 +1,17 @@
+# pushed as costela/wesher-test to speed up testing
+
+FROM golang:1.12-alpine
+
+RUN apk update && apk add git make gcc
+RUN go get -d golang.zx2c4.com/wireguard \
+ && cd /go/src/golang.zx2c4.com/wireguard \
+ && rm donotuseon_linux.go \
+ && make install
+
+ENV WG_I_PREFER_BUGGY_USERSPACE_TO_POLISHED_KMOD=1
+
+COPY entrypoint.sh /
+
+WORKDIR /app
+
+ENTRYPOINT [ "/entrypoint.sh" ]