Use prompt instead of argv arguments in scripts

This makes it easier to handle truffle arguments which we for example
need to specify the network.
So we ask the user for input instead on using the argv array which might
change.

scripts/add-proposal.js

@@ -1,8 +1,9 @@
 const Registry = artifacts.require('./Registry.sol');
 const Operator = artifacts.require('./Operator.sol');
 const Contributors = artifacts.require('./Contributors.sol');
+const promptly = require('promptly');
 
-var bs58 = require('bs58');
+const bs58 = require('bs58');
 
 function getBytes32FromMultiash(multihash) {
   const decoded = bs58.decode(multihash);
@@ -22,12 +23,9 @@ module.exports = function(callback) {
     var operator = await Operator.at(operatorAddress);
     var contributors = await Contributors.at(contributorsAddress);
 
-    let recipientAddress = process.argv[4];
-    if(!recipientAddress) {
-      console.log('please provide an address');
-      process.exit();
-    }
-    let ipfsHash = process.argv[5] || 'QmQNA1hhVyL1Vm6HiRxXe9xmc6LUMBDyiNMVgsjThtyevs';
+    let recipientAddress = await promptly.prompt('Contributor address: ');
+    let ipfsHash = await promptly.prompt('IPFS hash (blank for default): ', { default: 'QmQNA1hhVyL1Vm6HiRxXe9xmc6LUMBDyiNMVgsjThtyevs' });
+
     let multihash = getBytes32FromMultiash(ipfsHash);
 
     let contributorId = await contributors.getContributorIdByAddress(recipientAddress);