don't stop when getting a compiler warning but print it as a warning

lib/contracts/compiler.js

@@ -83,7 +83,11 @@ class Compiler {
         self.logger.info("compiling contracts...");
         solcW.compile({sources: input}, 1, function (output) {
           if (output.errors) {
-            return callback(new Error("Solidity errors: " + output.errors).message);
+            if (output.errors.length === 1 && output.errors[0].indexOf('Warning:') >= 0) {
+              self.logger.warn(output.errors[0]);
+            } else {
+              return callback(new Error("Solidity errors: " + output.errors).message);
+            }
           }
           callback(null, output);
         });

test_app/app/contracts/simple_storage.sol

@@ -12,6 +12,10 @@ contract SimpleStorage {
     storedData = x;
   }
 
+  function set2(uint x, uint y) {
+    storedData = x;
+  }
+
   function get() constant returns (uint retVal) {
     return storedData;
   }