Repository.get_file_content should take a path or a content

[shrik450]

Currently, Repository.get_file_content takes a Content object as its first arg. This means that a user would have to use Repository.get_git_content first, filter through based on path, and then feed get_file_content that content object to get the file content. This is unnecessary work, as the endpoint only needs a file path. We should change the first arg to take either a string path or a content object.