Based docker build on alpine:edge image and included tests for the build

in the Dockerfile.
Updated README.md to include developer and testing instructions.
Removed old files and scripts for building and testing.

Signed-off-by: Joris Melchior <jmelchior@pivotal.io>

scripts/build

@@ -1,8 +0,0 @@
-#!/bin/bash
-
-set -e -u -x
-
-mkdir -p assets
-go build -o assets/check ./cmd/check
-go build -o assets/in ./cmd/in
-go build -o assets/out ./cmd/out

scripts/ci

@@ -1,19 +0,0 @@
-#!/bin/bash
-# vim: set ft=sh
-
-set -eu
-
-export GOPATH=$PWD/gopath
-export PATH=$GOPATH/bin:$PATH
-
-BUILD_DIR=$PWD/built-resource
-
-cd $GOPATH/src/github.com/concourse/github-release-resource
-
-go install github.com/concourse/github-release-resource/vendor/github.com/onsi/ginkgo/ginkgo
-
-CGO_ENABLED=1 ginkgo -race -r -p "$@"
-
-./scripts/build
-
-cp -a assets Dockerfile $BUILD_DIR

scripts/test

@@ -1,18 +0,0 @@
-#!/bin/bash
-
-set -e
-
-not_installed() {
-  ! command -v $1 > /dev/null 2>&1
-}
-
-github_release_resource_dir=$(cd $(dirname $0)/.. && pwd)
-
-if not_installed ginkgo; then
-  echo "# ginkgo is not installed! run the following command:"
-  echo "    go install github.com/onsi/ginkgo/ginkgo"
-  exit 1
-fi
-
-cd $github_release_resource_dir
-ginkgo -r -p