Adds release instructions (#460)

RELEASE.md

@@ -0,0 +1,40 @@
+# Feign Release Process
+
+This repo uses [semantic versions](http://semver.org/). Please keep this in mind when choosing version numbers.
+
+1. **Alert others you are releasing**
+
+   There should be no commits made to master while the release is in progress (about 10 minutes). Before you start
+   a release, alert others on [gitter](https://gitter.im/OpenFeign/feign) so that they don't accidentally merge
+   anything. If they do, and the build fails because of that, you'll have to recreate the release tag described below.
+
+1. **Push a git tag**
+
+   The tag should be of the format `release-N.M.L`, for example `release-8.18.0`.
+
+1. **Wait for Travis CI**
+
+   This part is controlled by [`travis/publish.sh`](travis/publish.sh). It creates a couple commits, bumps the version,
+   publishes artifacts, syncs to Maven Central.
+
+## Credentials
+
+Credentials of various kind are needed for the release process to work. If you notice something
+failing due to unauthorized, re-encrypt them using instructions at the bottom of the `.travis.yml`
+
+Ex You'll see comments like this:
+```yaml
+env:
+  global:
+  # Ex. travis encrypt BINTRAY_USER=your_github_account
+  - secure: "VeTO...
+```
+
+To re-encrypt, you literally run the commands with relevant values and replace the "secure" key with the output:
+
+```bash
+$ travis encrypt BINTRAY_USER=adrianmole
+Please add the following to your .travis.yml file:
+
+  secure: "mQnECL+dXc5l9wCYl/wUz+AaYFGt/1G31NAZcTLf2RbhKo8mUenc4hZNjHCEv+4ZvfYLd/NoTNMhTCxmtBMz1q4CahPKLWCZLoRD1ExeXwRymJPIhxZUPzx9yHPHc5dmgrSYOCJLJKJmHiOl9/bJi123456="
+```