use last part of contract file rather than 1st

lib/compiler.js

@@ -89,7 +89,9 @@ Compiler.prototype.compile = function(contractFiles) {
   var solidity = [], serpent = [];
 
   for (var i = 0; i < contractFiles.length; i++) {
-    var extension = contractFiles[i].split('.')[1];
+    var contractParts = contractFiles[i].split('.'),
+      extension = contractParts[contractParts.length-1]
+
     if (extension === 'sol') {
       solidity.push(contractFiles[i]);
     }