Update README.md

[wcalebgray]

After several hours trying to work around the user prompts in my CI environment, I dug in the code and found that if you set these environment variables, you can avoid the prompts. This should be very obvious to users in the documentation and not hidden in the code.

[jspizziri]

@wcalebgray,

I'd be best to include a codeblock example of this in addition to the documentation you added.

[Gl4di4torRr]

This is how it works. I put this in my gulpfile.js

process.env.IMAGE = 'sidekick';
process.env.PUSH = 1;

new GulpDocker(gulp, {
        sidekick: {
                name: "chrisbolton",
                dockerfile: ".",
                tags: ["1"],
                repo: "nexus.mycompany.com:8003/com/mycompany/devops/chrisbolton"
        }
});

[nahusha1987]

@wcalebgray I am seeing these on the console after introducing the env variables

double free or corruption (out) SIGABRT: abort PC=0x7fef69757e97 m=0 sigcode=18446744073709551610 signal arrived during cgo execution

goroutine 1 [syscall, locked to thread]: runtime.cgocall(0x4afd50, 0xc420047cc0, 0xc420047ce8) /usr/lib/go-1.8/src/runtime/cgocall.go:131 +0xe2 fp=0xc420047c90 sp=0xc420047c50 github.com/docker/docker-credential-helpers/secretservice._Cfunc_free(0xbcd920) github.com/docker/docker-credential-helpers/secretservice/_obj/_cgo_gotypes.go:111 +0x41 fp=0xc420047cc0 sp=0xc420047c90 github.com/docker/docker-credential-helpers/secretservice.Secretservice.List.func5(0xbcd920) /build/golang-github-docker-docker-credential-helpers-cMhSy1/golang-github-docker-docker-credential-helpers-0.5.0/obj-x86_64-linux-gnu/src/github.com/docker/docker-credential-helpers/secretservice/secretservice_linux.go:96 +0x60 fp=0xc420047cf8 sp=0xc420047cc0 github.com/docker/docker-credential-helpers/secretservice.Secretservice.List(0x0, 0x756060, 0xc4200702c0) /build/golang-github-docker-docker-credential-helpers-cMhSy1/golang-github-docker-docker-credential-helpers-0.5.0/obj-x86_64-linux-gnu/src/github.com/docker/docker-credential-helpers/secretservice/secretservice_linux.go:97 +0x217 fp=0xc420047da0 sp=0xc420047cf8 github.com/docker/docker-credential-helpers/secretservice.(*Secretservice).List(0x77e548, 0xc420047e88, 0x410022, 0xc420070220) :4 +0x46 fp=0xc420047de0 sp=0xc420047da0 github.com/docker/docker-credential-helpers/credentials.List(0x756ba0, 0x77e548, 0x7560e0, 0xc42008e008, 0x0, 0x10) /build/golang-github-docker-docker-credential-helpers-cMhSy1/golang-github-docker-docker-credential-helpers-0.5.0/obj-x86_64-linux-gnu/src/github.com/docker/docker-credential-helpers/credentials/credentials.go:145 +0x3e fp=0xc420047e68 sp=0xc420047de0 github.com/docker/docker-credential-helpers/credentials.HandleCommand(0x756ba0, 0x77e548, 0x7ffefef7d7bb, 0x4, 0x7560a0, 0xc42008e000, 0x7560e0, 0xc42008e008, 0x40e398, 0x4d35c0) /build/golang-github-docker-docker-credential-helpers-cMhSy1/golang-github-docker-docker-credential-helpers-0.5.0/obj-x86_64-linux-gnu/src/github.com/docker/docker-credential-helpers/credentials/credentials.go:60 +0x16d fp=0xc420047ed8 sp=0xc420047e68 github.com/docker/docker-credential-helpers/credentials.Serve(0x756ba0, 0x77e548) /build/golang-github-docker-docker-credential-helpers-cMhSy1/golang-github-docker-docker-credential-helpers-0.5.0/obj-x86_64-linux-gnu/src/github.com/docker/docker-credential-helpers/credentials/credentials.go:41 +0x1cb fp=0xc420047f58 sp=0xc420047ed8 main.main() /build/golang-github-docker-docker-credential-helpers-cMhSy1/golang-github-docker-docker-credential-helpers-0.5.0/secretservice/cmd/main_linux.go:9 +0x4f fp=0xc420047f88 sp=0xc420047f58 runtime.main() /usr/lib/go-1.8/src/runtime/proc.go:185 +0x20a fp=0xc420047fe0 sp=0xc420047f88 runtime.goexit() /usr/lib/go-1.8/src/runtime/asm_amd64.s:2197 +0x1 fp=0xc420047fe8 sp=0xc420047fe0

goroutine 17 [syscall, locked to thread]: runtime.goexit() /usr/lib/go-1.8/src/runtime/asm_amd64.s:2197 +0x1

rax 0x0 rbx 0x7ffefef7cef0 rcx 0x7fef69757e97 rdx 0x0 rdi 0x2 rsi 0x7ffefef7cc80 rbp 0x7ffefef7cff0 rsp 0x7ffefef7cc80 r8 0x0 r9 0x7ffefef7cc80 r10 0x8 r11 0x246 r12 0x7ffefef7cef0 r13 0x1000 r14 0x0 r15 0x30 rip 0x7fef69757e97 rflags 0x246 cs 0x33 fs 0x0 gs 0x0