added mappings to default build.gradle

fml/install/build.gradle

@@ -24,6 +24,13 @@ archivesBaseName = "modid"
 minecraft {
     version = "${version}"
     runDir = "eclipse"
+    
+    // the mappings can be changed at any time, and must be in the following format.
+    // snapshot_YYYYMMDD   snapshot are built nightly.
+    // stable_#            stables are built at the discretion of the MCP team.
+    // Use non-default mappings at your own risk. they may not allways work.
+    // simply re-run your setup task after changing the mappings to update your workspace.
+    mappings = "${mappings}"
 }
 
 dependencies {