chore: Migrate to go module

also executing the below

```
$ go mod init
$ go mod download
```

.circleci/config.yml

@@ -3,22 +3,18 @@ jobs:
   build:
     docker: &docker
       - image: circleci/golang:1.11
-    working_directory: /go/src/github.com/tsub/s3-edit
+        environment:
+          GO111MODULE: "on"
     steps:
       - checkout
-      - run: &vendoring
-          name: Vendoring go packages
-          command: dep ensure
       - run:
           name: Run tests
           command: go test ./...
 
   deploy:
     docker: *docker
-    working_directory: /go/src/github.com/tsub/s3-edit
     steps:
       - checkout
-      - run: *vendoring
       - deploy:
           name: Release
           command: curl -sL https://git.io/goreleaser | bash

README.md

@@ -88,5 +88,6 @@ Edited with s3-edit.
 ### How to setup
 
 ```
-$ go get -u github.com/tsub/s3-edit
+$ git clone git@github.com:tsub/s3-edit.git
+$ export GO111MODULE=on
 ```

go.mod

@@ -0,0 +1,19 @@
+module github.com/tsub/s3-edit
+
+require (
+	github.com/aws/aws-sdk-go v1.10.31
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/go-ini/ini v1.28.2 // indirect
+	github.com/gopherjs/gopherjs v0.0.0-20180825215210-0210a2f0f73c // indirect
+	github.com/inconshreveable/mousetrap v1.0.0 // indirect
+	github.com/jmespath/go-jmespath v0.0.0-20151117175822-3433f3ea46d9 // indirect
+	github.com/jtolds/gls v4.2.1+incompatible // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/smartystreets/assertions v0.0.0-20180820201707-7c9eb446e3cf // indirect
+	github.com/smartystreets/goconvey v0.0.0-20180222194500-ef6db91d284a // indirect
+	github.com/spf13/cobra v0.0.0-20170823073209-2df9a5318133
+	github.com/spf13/pflag v1.0.0 // indirect
+	github.com/stretchr/testify v1.2.2 // indirect
+	golang.org/x/net v0.0.0-20180826012351-8a410e7b638d // indirect
+	golang.org/x/text v0.3.0 // indirect
+)

go.sum

@@ -0,0 +1,30 @@
+github.com/aws/aws-sdk-go v1.10.31 h1:Zc1V0n1VZ2DmCgBpiG1VLiUaGeOaq0GLFtQdCqo7TvE=
+github.com/aws/aws-sdk-go v1.10.31/go.mod h1:ZRmQr0FajVIyZ4ZzBYKG5P3ZqPz9IHG41ZoMu1ADI3k=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-ini/ini v1.28.2 h1:drmmYv7psRpoGZkPtPKKTB+ZFSnvmwCMfNj5o1nLh2Y=
+github.com/go-ini/ini v1.28.2/go.mod h1:ByCAeIL28uOIIG0E3PJtZPDL8WnHpFKFOtgjp+3Ies8=
+github.com/gopherjs/gopherjs v0.0.0-20180825215210-0210a2f0f73c h1:16eHWuMGvCjSfgRJKqIzapE78onvvTbdi1rMkU00lZw=
+github.com/gopherjs/gopherjs v0.0.0-20180825215210-0210a2f0f73c/go.mod h1:wJfORRmW1u3UXTncJ5qlYoELFm8eSnnEO6hX4iZ3EWY=
+github.com/inconshreveable/mousetrap v1.0.0 h1:Z8tu5sraLXCXIcARxBp/8cbvlwVa7Z1NHg9XEKhtSvM=
+github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
+github.com/jmespath/go-jmespath v0.0.0-20151117175822-3433f3ea46d9 h1:1SlajWtS+u/6x2Be5vrHyrbSxkeIf/+ISBu//kmjpnc=
+github.com/jmespath/go-jmespath v0.0.0-20151117175822-3433f3ea46d9/go.mod h1:Nht3zPeWKUH0NzdCt2Blrr5ys8VGpn0CEB0cQHVjt7k=
+github.com/jtolds/gls v4.2.1+incompatible h1:fSuqC+Gmlu6l/ZYAoZzx2pyucC8Xza35fpRVWLVmUEE=
+github.com/jtolds/gls v4.2.1+incompatible/go.mod h1:QJZ7F/aHp+rZTRtaJ1ow/lLfFfVYBRgL+9YlvaHOwJU=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/smartystreets/assertions v0.0.0-20180820201707-7c9eb446e3cf h1:6V1qxN6Usn4jy8unvggSJz/NC790tefw8Zdy6OZS5co=
+github.com/smartystreets/assertions v0.0.0-20180820201707-7c9eb446e3cf/go.mod h1:OnSkiWE9lh6wB0YB77sQom3nweQdgAjqCqsofrRNTgc=
+github.com/smartystreets/goconvey v0.0.0-20180222194500-ef6db91d284a h1:JSvGDIbmil4Ui/dDdFBExb7/cmkNjyX5F97oglmvCDo=
+github.com/smartystreets/goconvey v0.0.0-20180222194500-ef6db91d284a/go.mod h1:XDJAKZRPZ1CvBcN2aX5YOUTYGHki24fSF0Iv48Ibg0s=
+github.com/spf13/cobra v0.0.0-20170823073209-2df9a5318133 h1:k5T0NKT0QzMzEaqufAzrZjPlFdCuPwXlngPZlLehiJU=
+github.com/spf13/cobra v0.0.0-20170823073209-2df9a5318133/go.mod h1:1l0Ry5zgKvJasoi3XT1TypsSe7PqH0Sj9dhYf7v3XqQ=
+github.com/spf13/pflag v1.0.0 h1:oaPbdDe/x0UncahuwiPxW1GYJyilRAdsPnq3e1yaPcI=
+github.com/spf13/pflag v1.0.0/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
+github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
+github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+golang.org/x/net v0.0.0-20180826012351-8a410e7b638d h1:g9qWBGx4puODJTMVyoPrpoxPFgVGd+z1DZwjfRu4d0I=
+golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=