Use go mod and separate packages

[migueleliasweb]

The purposed new structure looks like this:

Changes:

• Use go mod for reliable builds and ease of development
• New packages
• New overall structure that adheres closer to: https://github.com/golang-standards/project-layout
• Small changes to the Dockerfile

.
├── computer.csv
├── docker-compose.yml
├── Dockerfile
├── go.mod
├── go.sum
├── internal
│   ├── repository
│   │   ├── data.go
│   │   └── types.go
│   └── wol
│       └── wol.go
├── LICENSE
├── main.go
├── pages
│   └── index.html
├── pkg
│   ├── cmd
│   │   ├── const.go
│   │   ├── envVars.go
│   │   └── shellArgs.go
│   └── http
│       └── handler
│           ├── pages.go
│           ├── rest.go
│           └── types.go
├── README.md
├── screenshot.PNG
└── VERSION

[migueleliasweb]

Regarding #20

[migueleliasweb]

Related to: sabhiram/go-wol#20