Fix config file generation call in README

[ChefAustin]

Description

If you run chef-load init > chef-load.toml (as the README.md dictates) you end up with a chef-load.toml file that looks like this:

Usage of chef-load:

AFAICT, this is just a typo and one should really be using the -sample-config flag.

## Related Issue
Not necessary.

## Types of changes
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing functionality to change)
- [x] Chore (non-breaking change that does not add functionality or fix an issue)

## Checklist:
<!--- Go over all the following points, and put an `x` in all the boxes that apply. -->
<!--- If you're unsure about any of these, don't hesitate to ask. We're here to help! -->
- [ This document doesn't actually exist ] I have read the **CONTRIBUTING** document.
- [x] I have run the pre-merge tests locally and they pass.
- [x] I have updated the documentation accordingly.
- [x] I have added tests to cover my changes.
- [x] All new and existing tests passed.
- [x] All commits have been signed-off for [the Developer Certificate of Origin](https://github.com/chef/chef/blob/master/CONTRIBUTING.md#developer-certification-of-origin-dco).

[tas50]

Merging under the obvious fix rule for readme changes