OpenNetVM v18.05 (#258)

Updates release document with notes about OpenNetVM v18.05

Commit log:

* Release notes 18.05

* add docker info

* Add link to docker docs

* Add Docker to title and add Good First Issue note

docs/Releases.md

@@ -13,6 +13,21 @@ use a date based versioning system.  Now, a release version can look
 like `17.11` where the "major" number is the year and the "minor" number
 is the month.
 
+#### v18.05 (5/31/18): Bug Fixes, Latency Measurements, and Docker Image
+This release adds a feature to the Speed Tester example NF to support latency measurements by using the `-l` flag. Latency is calculated by writing a timestamp into the packet body and comparing this value when the packet is returned to the Speed Tester NF. A sample use case is to run 3 speed tester NFs configured to send in a chain, with the last NF sending back to the first. The first NF can use the `-l` flag to measure latency for this chain. Note that only one NF in a chain should be using the flag since otherwise timestamp information written to the packet will conflict. 
+
+It also makes minor changes to the setup scripts to work better in NSF CloudLab environments.
+
+We now provide a docker container image that can be used to easily run NFs inside containers. See the [Docker Docs](./Docker.md) for more information.
+
+OpenNetVM support has now been integrated into the mainline [mTCP repository](https://github.com/eunyoung14/mtcp).
+
+Finally, we are now adding issues to the GitHub Issue Tracker with the [Good First Issue](https://github.com/sdnfv/openNetVM/issues?q=is%3Aissue+is%3Aopen+label%3A%22good+first+issue%22) label to help others find ways to contribute to the project. Please take a look and contribute a pull request!
+
+An NSF CloudLab template including OpenNetVM 18.05, mTCP, and some basic networking utilities is available here: https://www.cloudlab.us/p/GWCloudLab/onvm-18.05
+
+*No API changes were introduced in this release.*
+
 #### v18.03 (3/27/18): Updated DPDK and preliminary mTCP support
 This release updates the DPDK submodule to use version 17.08.  This DPDK update caused breaking changes to its API, so updates have been made to the OpenNetVM manager and example NFs to support this change.