Add command line arguments using commander

What I'd like to have:

```bash
git bump patch
```

This will bump **the patch value** of your latest git tag.
Ex: v1.0.0 -> v1.0.1

```bash
git bump minor
```

This will bump **the minor value** of your latest git tag.
Ex: v1.0.0 -> v1.1.0

```bash
git bump major
```

This will bump **the major value** of your latest git tag.
Ex: v1.0.0 -> v2.0.0