Change some texts to links in README

README.md

@@ -74,7 +74,7 @@ documentation useful ([ARCHITECTURE.md](ARCHITECTURE.md)).
 Cargo is primarily distributed under the terms of both the MIT license
 and the Apache License (Version 2.0).
 
-See LICENSE-APACHE and LICENSE-MIT for details.
+See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT) for details.
 
 ### Third party software
 
@@ -85,7 +85,7 @@ In binary form, this product includes software that is licensed under the
 terms of the GNU General Public License, version 2, with a linking exception,
 which can be obtained from the [upstream repository][1].
 
-See LICENSE-THIRD-PARTY for details.
+See [LICENSE-THIRD-PARTY](LICENSE-THIRD-PARTY) for details.
 
 [1]: https://github.com/libgit2/libgit2