support searching for local package.json

When including a package that uses aliasify as a dependency, aliasify attempts to read the aliasify configuration from the root `package.json` instead of the dependency `package.json`. For example, given the following directory structure:

```
- my_package
    - package.json
    - node_modules
        - package_using_aliasify
            - package.json
            - node_modules
                - aliasify
```

Aliasify will attempt to read the `aliasify` object from `my_package/package.json` instead of `my_package/node_modules/package_using_aliasify/package.json`. This pull request adds the `fromSourceFileDir: true` flag when calling `makeRequireTransform` so that browserify transform tools knows to search for the closest `package.json` instead of the root one.