Add bors integration

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index 55492aa..69d3a37 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,3 +1,10 @@
+branches:
+  only:
+    # This is where pull requests from "bors r+" are built.
+    - staging
+    # This is where pull requests from "bors try" are built.
+    - trying
+
 language: rust
 rust:
   - nightly-2019-11-06

CONTRIBUTING.md

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..bbad037
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,8 @@
+# PR Workflow
+
+We use the bors-ng bot to merge PRs. In short, when someone replies `bors r+`,
+your PR has been scheduled for final tests and will be automatically merged. If
+a maintainer replies `bors delegate+`, then you have been granted the authority
+to merge your own PR (usually this will happen if there are some trivial
+changes required). For a full list of bors commands,
+[see the bors documentation](https://bors.tech/documentation/).

bors.toml

diff --git a/bors.toml b/bors.toml
new file mode 100644
index 0000000..b59819f
--- /dev/null
+++ b/bors.toml
@@ -0,0 +1,3 @@
+status = [
+  "continuous-integration/travis-ci/push"
+]
\ No newline at end of file