Example should specify -g repo should exist, other possibilities

[jasonhemann]

This wasn't initially clear to me from the documentation.

Because this may not be completely obvious, I'd suggest saying to leave the .jar file in the directory in which it's unzipped, or to add the ./vendors/ subdir to classpath.

I think also a slightly more complex example would help clarify usage some.

java -jar 
      ./path/to/git-lfs-migrate.jar  \ #should be in same location as vendors 
      -s ./the/path/for/source-repo.git \
      -d ./and/path/for/destination-repo.git \ 
      -g git@my.github.url.com:username/public-repo-name.git \ #this empty repo should already exist 
        \ # ^-- for instance git@github.com:bozaro/my-new-repo.git 
     "*.pet" \ # and as many extensions as you like 
     "*.cat" \
     "*.dog"