title: Where and why add repositories on build.gradle
body: <p>When Android Studio creates a project, the top-level build file has two repositories definitions, one inside <em>buildscript</em> and another inside <em>allprojects</em>.</p>
  
  <pre><code>// Top-level build file where you can add configuration options common to all sub-    projects/modules.
  
  buildscript {
      repositories {
          mavenCentral()
      }
      dependencies {
          classpath 'com.android.tools.build:gradle:0.9.+'
      }
  }
  
  allprojects {
      repositories {
          mavenCentral()
      }
  }
  </code></pre>
  
  <p>Where must I add another repository and why?</p>
  
  <p>I think that repository inside buildscript is here to add the gradle plugin dependency, but I'm not sure...</p>
  
  <p>Someone could clarify me, please.</p>
  
  <p>Thank you!</p>