Can we just provide the schema path in the plugin?

[benhowes]

see:

tavern-flask/tavern_flask/tavernhook.py

Lines 38 to 40 in 08231cf

	schema_path = join(abspath(dirname(__file__)), "schema.yaml")
	with open(schema_path, "r") as schema_file:
	schema = yaml.load(schema_file)

Can we cut down on the boilerplate in places like this by just passing a string from the hook?