README fix

Adding toolchain and updating documentation

Update install instructions from to `go install`

Looks like `go get` has been deprecated.

New method for installation is `go install <repo-url>@latest`

In this case:

```sh
go install github.com/qeesung/image2ascii@latest
```

Add Awesome badge

Update README.md

Update README.md

Update README.md

Update README.md

Update README.md

add some examples

Update README.md

Update the README.md

Update README.md

Update README.md

Update README.md

rename example directory to docs

Add Converalls Badge

Add Cover badge

Add godoc badge

Update README.md