title: sbt: Add multiple resolvers
body: <p>I tried to add two resolvers:</p>
  
  <pre><code>resolvers ++= Seq(
    Resolver.DefaultMavenRepositoryRoot,
    //Resolver.sonatypeRepo("releases"),
    Resolver.typesafeRepo("releases")
  )
  </code></pre>
  
  <p>However I keep getting:</p>
  
  <blockquote>
    <p>...build.sbt:9: error: No implicit for
    Append.Values[Seq[sbt.Resolver], Seq[java.io.Serializable]] found,<br>
    so Seq[java.io.Serializable] cannot be appended to Seq[sbt.Resolver]
    resolvers ++= Seq(
              ^ [error] Type error in expression Invalid response. Invalid response.</p>
    
    <p>Invalid response.</p>
  </blockquote>
  
  <ol>
  <li>What are the default resolvers in the <code>resolvers</code>?</li>
  <li>What is wrong? How to add multiple resolvers ?</li>
  </ol>