Merge pull request #1616 from ethereum/yann300-patch-6

Update example-contracts.js, add pragma

src/app/editor/example-contracts.js

@@ -1,6 +1,7 @@
 'use strict'
 
-var ballot = `contract Ballot {
+var ballot = `pragma solidity >=0.4.22 <0.6.0;
+contract Ballot {
 
     struct Voter {
         uint weight;