Get contributor by ID

Co-Authored-By: skddc <sebastian@kip.pe>

lib/contracts/contribution.js

@@ -27,6 +27,9 @@ class Contribution extends Base {
   }
 
   getByContributorId(contributorId) {
+    return this.functions.getContributorAddressById(contributorId)
+      .then(address => this.getByContributorAddress(address));
+  }
     // return this.functions.balanceOf(address)
     //   then(balance => {
     //     count = balance.toNumber();