Golang runtime (#125)

Minimal golang runtime.  

Functions are built as Go plugins, and the plugin is uploaded to fission.

See `environments/go/README.md` for instructions and `examples/go` for a usage example.

For now, we're re-using the 'code' field of the function to store the binary plugin. With v2 environments, this will be stored separately as a binary package.

environments/go/Dockerfile

@@ -0,0 +1,14 @@
+FROM golang:1.8
+
+ENV GOPATH /usr
+ENV APP	   ${GOPATH}/src/github.com/fission/fission/environments/go
+
+ADD context	    ${APP}/context
+ADD server.go   ${APP}
+
+WORKDIR ${APP}
+RUN go get
+RUN go build -o /server server.go
+
+ENTRYPOINT ["/server"]
+EXPOSE 8888