Fixes issue with migrations not being found when relative path for the m...

...igrations folder is provided.

This is because:

```
this.path           = path.normalize(p)
```

Does not resolve the relative path correctly, we could use something like this:

```
optionsFilePath = path.join(process.cwd(), program.optionsPath)
```

Which is used in the `./bin/sequelize` CLI commands file, but:

```
this.path           = path.resolve(p)
```

Does the work for us and works with absolute and relative routes, also works correctly when no migrations directory path is specified.