title: "release" command from sbt-release plugin is not recognized
body: <p>I can't get the sbt-release plugin to work at all. The "sbt release" command is not recognized.</p>
  
  <p>As per plugin's documentation, I have this entry added to my ./project/plugins.sbt file in my play application:</p>
  
  <pre><code>addSbtPlugin("com.github.gseitz" % "sbt-release" % "0.8.5")
  </code></pre>
  
  <p>And I'm running the latest to-date 0.13.6 version of sbt launcher. Here's the error that I get when I execute "sbt release" from my project directory:</p>
  
  <pre><code>[info] Loading project definition from /Users/Projects/project
  [info] Loading [pom.xml]
  [info] Use auto-generated Build object
  [success] POM definition loaded
  [info] Set current project to integration (in build file:/Users/Projects/project/)
  [error] Not a valid command: release (similar: reload, eclipse, last)
  [error] Not a valid project ID: release
  [error] Expected ':' (if selecting a configuration)
  [error] Not a valid key: release (similar: rpmRelease, rpm-release, resolvers)
  [error] release
  [error]        ^
  </code></pre>
  
  <p>And just to make sure, that sbt-release plugin does get loaded into the project, I execute "sbt about", and it does show that sbt-release is in the list of Available Plugins. But again, for some reason, "sbt release" command is not recognized.</p>
  
  <pre><code>&gt; sbt about
  ...
  [info] Available Plugins: ... sbtrelease.ReleasePlugin, ...
  </code></pre>