Update Dockerfile to pull released artifact rather.

With changes made using govvv and goreleaser it is now required
that the docker build pull the released binary from GH. This also
means the docker image uses a source of truth binary rather than
building from a checked out VCS which could be different code from
the released version if human error occurs.

Dockerfile

@@ -1,13 +1,21 @@
-FROM golang:alpine as builder
+FROM alpine:latest
 
-WORKDIR /go/src/github.com/jrasell/levant
-COPY . .
-RUN apk add --no-cache make \
-    && make install
+LABEL maintainer James Rasell<(jamesrasell@gmail.com> (@jrasell)
+LABEL vendor "jrasell"
 
-FROM alpine:latest
+ENV LEVANT_VERSION 0.1.1
+
+WORKDIR /usr/bin/
 
-RUN apk add --no-cache ca-certificates
+RUN buildDeps=' \
+                bash \
+                wget \
+        ' \
+        set -x \
+        && apk --no-cache add $buildDeps ca-certificates \
+        && wget -O levant https://github.com/jrasell/levant/releases/download/${LEVANT_VERSION}/linux-amd64-levant \
+        && chmod +x /usr/bin/levant \
+        && apk del $buildDeps \
+        && echo "Build complete."
 
-COPY --from=builder /go/bin/levant /usr/bin/levant
 CMD ["levant", "--help"]