Missing LICENSE file and Cargo.toml entry

[robinhundt]

According to the comment at the top of the lib.rs file, the PACT data-model implementation is MIT licensed. However, the repository is missing a LICENSE file and an according entry in the Cargo.toml.

pact-data-model/src/lib.rs

Lines 1 to 6 in df8c382

	/*
	* Copyright (c) Martin Pompéry
	*
	* This source code is licensed under the MIT license found in the
	* LICENSE file in the crate's root directory of this source tree.
	*/