Expect newlines in output after linting commit messages

When I try to merge more than two branches, commitlint will print its output before git's diff info. Then git will continue to print its output but without a newline.

## Current Behavior


```bash
▶ git merge dev_name_A dev_name_B
Fast-forwarding to: dev_name_A
Trying simple merge with dev_name_B
Simple merge did not work, trying automatic merge.
Auto-merging package-lock.json
Auto-merging package.json
husky > commit-msg (node v10.12.0)

⧗   input: Merge branches 'dev_name_A' and 'dev_name_B' into dev_name_C
✔   found 0 problems, 0 warningsMerge made by the 'octopus' strategy.
 build/prod.js                                                         |   2 +-

 ...any other diff info
```

## Expected Behavior


```bash
⧗   input: Merge branches 'dev_name_A' and 'dev_name_B' into dev_name_C
✔   found 0 problems, 0 warnings

Merge made by the 'octopus' strategy.
 build/prod.js                                                         |   2 +-

 ...any other diff info
```

## Affected packages
* [x] cli
* [ ] core
* [ ] prompt
* [ ] config-angular

## Possible Solution


Print additional newlines after printing commitlint's output.

## Steps to Reproduce (for bugs)


1. Create three git chunks.
2. Merge two of those chunks into another chunk.

<details>
  <summary>commitlint.config.js</summary>
  
  

```js
module.exports = {
    extends: ['@commitlint/config-conventional'],
    rules: {
        'scope-empty': [2, 'never'],
        'scope-enum': [2, 'always', [
            'scope-A',
            'scope-B',
        ]],
        'subject-empty': [2, 'never'],
        'subject-case': [0, 'never'],
    },
};
```

</details>

## Context



## Your Environment


| Executable | Version |
| ---: | :--- |
| `commitlint --version` | 7.2.1 |
| `git --version`  | 2.19.2 |
| `node --version` | v10.12.0 |

| Others | Version |
| :--- | :--- |
| husky | 1.2.0 |
| os  | macOS Mojave 10.14.1 |

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Expect newlines in output after linting commit messages #504

Current Behavior

Expected Behavior

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Possible Solution

Steps to Reproduce (for bugs)

Context

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Executable	Version
`commitlint --version`	7.2.1
`git --version`	2.19.2
`node --version`	v10.12.0