Fixed builder image and added docs for it

.dockerignore

@@ -1,2 +1,3 @@
 bin
 vendor
+pkg

Dockerfile.build.alpine

@@ -5,5 +5,5 @@ RUN apk-install bash go bzr git mercurial subversion openssh-client ca-certifica
 RUN mkdir -p /go/src /go/bin && chmod -R 777 /go
 ENV GOPATH /go
 ENV PATH /go/bin:$PATH
-WORKDIR /go
+WORKDIR /app
 RUN go get github.com/constabulary/gb/...

docs/installation.md

@@ -23,6 +23,16 @@ $ ./build
 $ sudo ./install
 ```
 
+#### Building from Source for Alpine Linux
+
+Since many people are using Alpine Linux as their base images for Docker there's support to build Alpine package also. Naturally by using Docker itself. :)
+
+```
+$ docker build -t confd_builder -f Dockerfile.build.alpine .
+$ docker run -ti -v $(pwd):/app confd_builder ./build
+```
+The above docker commands will produce binary in the local bin directory.
+
 ### Next Steps
 
 Get up and running with the [Quick Start Guide](quick-start-guide.md).