Implement a tag function from local file system

[faiq]

according to the documentation here you are able to make requests to the tag parameter with a local file, but this functionallity is not availble in this client. it seems to be implemented in the python client here. i'll be willing to put in a pull request.

[samuelcouch]

You are correct, that wasn't implemented. A PR would be much appreciated! :+1:

[zquestz]

This is merged into my fork: https://github.com/zquestz/clarifai-go