chore(.github/CONTRIBUTING): fix typos and URLs

.github/CONTRIBUTING.md

@@ -1,15 +1,15 @@
 # Contributing to Lean
 
-Thank you for choosing to contribute to Lean, this document is a intended as a brief guide
+Thank you for choosing to contribute to Lean. This document is intended as a brief guide
 for new contributors to help streamline the process and make it as easy as possible
 for you (the contributors) and us (the maintainers).
 
 ### Writing Code
 
-- [Coding Style](doc/coding_style.md)
-- [Library Style Conventions](doc/lean/library_style.org)
-- [Git Commit Conventions](doc/commit_convention.md)
-- [Automatic Builds](doc/make/travis.md)
+- [Coding Style](../doc/coding_style.md)
+- [Library Style Conventions](../doc/lean/library_style.org)
+- [Git Commit Conventions](../doc/commit_convention.md)
+- [Automatic Builds](../doc/make/travis.md)
 
 # Opening Issues
 
@@ -27,7 +27,7 @@ So, here are some guidelines for submitting PRs:
 - Small bug fixes are always welcome.
 - Before implementing a major feature or refactoring the code, please ask whether the change is welcome or not.
   The worst kind of PR is the "unwanted one". That is, we don’t want it, but we have to explain why we will not merge it.
-- Ensure all test suite works before submitting a PR. You can run the test suite (after building Lean and the Lean library) by calling `ctest` in your build directory.
+- Ensure all tests work before submitting a PR. You can run the test suite (after building Lean and the Lean library) by calling `ctest` in your build directory.
 - Ensure your Pull Request meets the coding and commit conventions documented above.
 - Ensure your Pull Request contains tests for the behavior, for both features or
   bug fixes.