Mkdocs-material-extensions

- **FIX**: No longer specify `mkdocs-material` as a dependency as `mkdocs-material` specifies these extensions as a
dependency. This created a circular dependency. While `pip` has no issues with such scenarios, this created issues
for some versioning packages. `mkdocs-material` (the only package this works with) will now manage which version of
`mkdocs-material-extensions` it needs.

- **FIX**: Ensure we don't modify the original icon path setting.

- **NEW**: First stable release.