Add release instructions (because I always forget)

README.markdown

@@ -5,17 +5,27 @@ Scala code.
 
 # Patch Policy
 
-Patches are gladly accepted from their original author. 
+Patches are gladly accepted from their original author.
 
-Along with any patches, please state that the patch is your original work 
+Along with any patches, please state that the patch is your original work
 and that you license the work to the ScalaJPA project under the project's
- open source license.
+open source license.
+
+# Releasing
+
+To build across all configured Scala versions, run
+
+    sbt '+ publish'
+
+This will require a signing key and credentials to publish to staging at
+SonaType. In general, follow the instructions at
+http://central.sonatype.org/pages/producers.html.
 
 # License
 
-Copyright © 2008-2016 Derek Chen-Becker 
+Copyright © 2008-2016 Derek Chen-Becker
 
-Licensed under the Apache License, Version 2.0 (the "License"); 
+Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 
@@ -25,4 +35,8 @@ Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions
-and limitations under the License. 
+and limitations under the License.
+
+<!-- Local Variables: -->
+<!-- fill-column: 80 -->
+<!-- End: -->