Remove bundle command

They were replaced by IOStreams struct.

`bundle` command was never really used and since now there is an `init`
command, reimplementing ...

Add tests for commands that manipulate changelog file

Improve error handling for release command

Refactor show command and add tests

Refactor `show` command and write tests for it, while also improving
the error handling.

Refactor release command and add tests

Add init command

Fix coverage badge

Refactor fmt command to be testable

This will gradually replace `inputFile` and `outputFile` in
sub-commands.

Avoid the usage of globals when possible

Prefer to grab options from `cmd.Flags()` instead.

Change parser.Parser interface to accept io.Reader

No need to use `bytes.Buffer` since we moved to
`buffio` package.

Refactor commands to simplify usageinput/output handling

Use `PersistentPreRun` and `PersistentPostRun` to open files for read
and write and flush conten...

Fix blackfriday import

Update import path for russross/blackfriday

Update dependencies to latest version

Replace old gometalinter.v2 with golangci-lint

Replace dep with Go modules

Since the project was replaced by golangci-lint, this disables
the check in CI until we proper r...

Dependencies will be managed by modules alone.

Go will manage dependencies automatically with using modules.

Add commands to manipulate the changelog

Add command 'added' to manipulate changelog

Do not submit coverage reports on forks

Avoids the error from goreleaser because the binary already exists.

Add gometalinter to Make and CI

Enable test coverage report