Fix a link in the pull request template (#399)

Author: dotemacs

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,7 +1,7 @@
 Before submitting a PR make sure the following things have been done (and denote this
 by checking the relevant checkboxes):
 
-- [ ] The commits are consistent with our [contribution guidelines](CONTRIBUTING.md)
+- [ ] The commits are consistent with our [contribution guidelines](./CONTRIBUTING.md)
 - [ ] You've added tests (if possible) to cover your change(s)
 - [ ] All tests are passing (run `lein do clean, test`)
 - [ ] Code inlining with mranderson works and tests pass with inlined code (run `./build.sh install` -- takes a long time)